FLUID's blog

Mazda 6–Throttle body ground

2011-07-25T10:03:00.001-07:00

Well, this can be one of those mods which don’t add any value, and in fact there is a long debate on forum on how useful it is. But it cost me ~10$ so why not. And besides, I felt immediate improvement in throttle response (but that could be just in my mind). Anyway…

You’ll need:

8mm and 10mm wrenches
4 AWG wire + connectors (I got preassembled wire from NAPA with connectors and stuff for 6.99 + tax)
Cable housing, some cable ties

Procedure is dead-simple: take the wire, wrap in cable housing, fasten with some cable ties, connect one side to the body (where your negative battery is connected), and another side to one of the throttle body bolt. You’re done. Pics below:

Mazda 6–How to clean throttle body

2011-07-22T13:00:00.001-07:00

Today I’ll tell how to clean throttle body on Mazda 6i 2008. But, as usual, disclaimer:

I’m not responsible for any damage you may cause to your car or, even worse, to yourself using instructions provided bellow. I’m not a professional mechanic and whatnot, so use these instructions at your own risk. Read entire post first and be sure you understand everything before you start it. If you’re in doubt – seek professional help.

NOTE: Chemicals you’ll be using are extremely flammable and poisonous, so use your brain, work in well ventilated area, away from open fire and don’t spray anything on hot engine (you’ll injure yourself and set your engine on fire)! Don’t work on engine when its hot, you’ll have to disconnect the coolant hoses and you can get injured. Don’t spill coolant as it poisonous, especially for animals, your dog will die from kidney failure :(!

Dirty throttle body can cause all sorts of problems: “sticky gas pedal”, poor gas mileage and poor throttle response.

For this job you’ll need:

hex screwdriver
8mm & 10mm metric wrenches
needle nose pliers
Piece of plastic bag and couple of cable ties
Empty 1 gal. milk bottle
small brush (toothbrush, painting brush, any king of brush you don’t need)
Carb and choke cleaner (or throttle body cleaner)
Brake cleaner

Let’s get started.

Start by disconnecting the negative terminal off your battery.

Loosen two bolts holding intake hose (one on throttle body, and another one next to MAF sensor). You need to remove the hose that goes from intake hose (just squeeze the blue clip and slide it off).

Once the intake hose is removed, disconnect the throttle body position sensor. Slide the red clip a little bit and disconnect the TPS connector.

Disconnect the the upper coolant hose the goes to throttle body. Use needle nose pliers and slide off the clip that holds the hose. Than CAREFULY disconnect the hose. Use a small piece of plastic bag and cable tie to seal the open end of removed hose.

Now remove 4 bolts that hold throttle body (8mm wrench) – green arrows on picture below.

There is another lower coolant hose that goes from throttle body (red arrow on above image), you can reach that once you detach the throttle body. Do the same what you’ve done for upper hose.

This is how surge tank looks like inside (below). Cleanup that mess a little bit. Spray a little of carb cleaner on a rag and wipe it off (you won’t be able to remove everything though). Don’t spray carb cleaner inside surge tank!

And this is how your dirty throttle body may look like:

Now the fun part: get your carb cleaner, brake cleaner, brush and cut off the top of the milk bottle.

Cover the connector, coolant lines and remove rubber gasket from the throttle body (as carb cleaner dissolve it). Its better to replace the gasket each time you remove the throttle body, but I reused mine.

Now, spray good amount of carb cleaner inside the throttle body. Use brush to reach everywhere, clean it thoroughly. When its clean, spray the throttle body with brake cleaner, it will clean remaining carb cleaner.

DISPOSE USED CHEMICALS PROPERLY (or at least don’t dump it on the ground).

Clean TB:

Assemble everything in reverse order:

And you’re done!

Mazda 6–Replacing front fender inner liner

2011-07-22T10:00:00.001-07:00

Its hard to call a DIY or a guide, it just some random pics I took replacing mine… The other day I found out that my driver’s side fender liner has a big hole in it. Probably some big debris got caught between the wheel and liner and destroyed it. Not a big deal I’d say, but I really didn’t like it.

So I found a replacement line off eBay for 15$ shipped. And here is the replacement process

First of, disclaimer:

And pics :

New inner fender liner:

And the old one removed from the car:

And.. done

How to resize all images in Word document?

2011-07-17T18:52:00.001-07:00

Here’s a simple VBA macro that will resize all images in a Word document to 16 cm width preserving the aspect ratio.

Code Snippet
     Sub AllPictSize() 
    Dim targetWidth As Integer 
    Dim oShp As Shape 
    Dim oILShp As InlineShape 
  
    targetWidth = 16 
  
    For Each oShp In ActiveDocument.Shapes 
        With oShp 
            .Height = AspectHt(.Width, .Height, _ 
            CentimetersToPoints(targetWidth)) 
            .Width = CentimetersToPoints(targetWidth) 
        End With 
    Next 
  
    For Each oILShp In ActiveDocument.InlineShapes 
        With oILShp 
            .Height = AspectHt(.Width, .Height, CentimetersToPoints(targetWidth)) 
            .Width = CentimetersToPoints(targetWidth) 
        End With 
    Next 
End Sub 
  
Private Function AspectHt(ByVal origWd As Long, ByVal origHt As Long, ByVal newWd As Long) As Long 
    If origWd <> 0 Then 
        AspectHt = (CSng(origHt) / CSng(origWd)) * newWd 
    Else 
        AspectHt = 0 
    End If 
End Function 
   

Mazda 6 – 60K? Time to clean your throttle body!

2011-07-11T09:09:00.001-07:00

Check out the next post on how to DIY!

Sonata 2006 v6–Changing Spark Plugs

2011-06-05T00:20:00.001-07:00

First of all, disclaimer:

Stuff you’ll need:

Please refer to this post for most of the tools required;
In addition to that you’ll need 10, 12, 14 mm sockets
needle nose pliers

Well, here are couple useful links from hmaservice.com that contain some information on how to remove intake manifold and spark plugs. This post is not a replacement and its recommended to use official manual as primary source, but those links below are not compete (some steps are missing, some are irrelevant and can be accomplished in a different way):

OK, let’s start.

Pop up the hood and disconnect the battery’s negative terminal. Using the 10mm socket remove engine cover:

Remove brackets that hold engine cover, you’ll need 10mm socket and needle nose pliers to detach wires, blue arrows are pointing to the places where those wires are attached. Just squeeze them with pliers and push them through.

Loosen spring clamps securing hose coming from airbox to throttle body (red arrows). Use pliers to squeeze the spring clamp on a breather hose, slide it off and disconnect breather hose (yellow arrow). Do not disconnect mass airflow sensor connector (green circle), just unfasten the airbox cover and leave it as is. Those connectors are pain in the *ss.. Remove the intake hose.

breather hose disconnected

“disconnect” oxygen sensor. Well, its not necessary to disconnect them, just slide them of the W-shaped bracket (surge tank stay), and leave them hanging.

Disconnect camshaft position sensor (in fact its not necessary, but it would be easier to move airbox cover, since MAF sensor is connected).

Slide off injector connector (left) and ignition coil connector (right) from its bracket and remove bracket (or leave it there).

Remove surge tank stay bolt (14 mm) and W-shaped bracket.

Yet, another connector (which must be the one for variable intake solenoid, but I’m not quite sure).

Disconnect manifold absolute pressure sensor (MAPS).

Remove 10mm bolt holding purge control solenoid valve in place (red arrow), disconnect its connector (yellow) and remove spring clamp and hose (blue one). Don’t disconnect another coming from it, disconnecting from surge tank is enough.

Time for throttle body. There are 3 10mm and one 12mm bolts holding it in place. Remove the bolts, don’t disconnect any harness or hoses as there are no reasons to do that (unless you want to). Be careful, as this ‘thing” is somewhat fragile…

Disconnect the two hoses (se below):

.. and there are couple more bolts to remove – 2 10mm and one 12mm at the back of the surge tank.

Now, the fun part – removing surge tank. There are 2 10mm bolts with with white rings on them and there another 3 10mm bolts and 2 nuts holding surge tank in place.

Once the surge tank is removed, cover intake manifold with some rag or towel immediately.

Now you have an access to the rear spark plugs(!).

Replacement procedure is straightforward for engines with coils, and I described it in details here, but in nutshell:
- Disconnect coil wire;
- Unscrew the bolt that keeps coil in place;
- Remove coil;
- Remove old plug;
- Take a new plug, put anti-seize lube on it and install it;
- Put a little of dielectric grease in coil, secure it with a bolt;
- Attach the wire;
- Repeat for all 6.

Once all plug are in place, reinstall everything in reverse order.

That’s pretty much it. Time start to finish: 3 hours (give or take half an hour).

Mazda 6 : Replacing spark plugs

2011-05-29T23:02:00.001-07:00

First of all, disclaimer:

Stuff you’ll need:

Spark plugs – Mazda 6i 2008 has ILTRA5-13G spark plugs – NGK Laser Iridium 3811 is a good replacement
Spark plug socket
Anti-seize lubricant
Dielectric grease
Torque wrench (optional, but highly recommended)
3/8 ratchet key and extension
8mm, 15mm keys

Let’s begin.

Disconnect battery’s negative terminal
Remove plastic cover from engine

Cleanup the area around ignition coils thoroughly, use whatever necessary (vacuum, toothbrush, etc) to make it clean, you don’t want any debris around when you remove your spark plugs.

Use 15 mm key to remove those little plastic thing that holds engine cover.

Disconnect coils wires.
Unscrew bolts that hold ignition coils
Remove coils

Now, take spark plug socket and remove a spark plug (I’d recommend doing one spark plug at a time)

Take new spark plug, put it in the socket
Apply small amount of anti-seize lube
And screw it back in place

Use torque wrench and tighten up spark plug to 8-17 ft-lb

last one….

Its time to reinstall ignition coils, but before you do, put small amount of dielectric grease in it.

All coils are in place

Put engine cover back in place and reconnect battery.
And, you’re done!

Before you throw away your old spark plugs inspect them for any signs of oil or white residue.

Don’t forget to setup your clock, radio, and power windows as those were reset when you disconnected the battery.

Mazda 6: Changing power steering fluid – the “turkey baster” way

2011-05-29T20:49:00.001-07:00

First of all, disclaimer:

Here is an easy way to do it without draining your power steering system completely. The idea is not mine, some guy from mazda6club.com came up with it, and all credits go to him.

For this task you’ll need:

turkey baster:

ATF M-V or equivalent (Dexron III) – 1 (or 2) 1 qrt bottles (depending on how dirty your current fluid is):

Steps:

Put your car on jack stands;

Put your key in ignition and turn it to the first or second position;
Pop up the hood and remove power steering fluid reservoir cap;

Take a turkey baster and remove 2 full basters of fluid from reservoir (when you do this first time, inspect the fluid, if its not nice and “pink-ish”, replace with 2 bottles, otherwise 1 is enough IMO);

Put new ATF in reservoir (exactly as many as you removed);
Turn steering wheel from lock to lock couple times;
Repeat #4-6 until all fluid is replaced;

Put the power steering reservoir cap back and lower the car;
Take used ATF to the recycling center

ATF, if spilled on paint, will damage it, so be careful, and wipe of any spills immediately.

Yet another MS interview…

2011-05-28T00:08:00.001-07:00

Well, it didn’t go well, in fact I wasn’t prepared at all.. Anyways, here are the questions I was asked, and if you think about them, they’re actually “easy-peasy”.. oh, well:

1st guy (SDE II):

Implement singleton, discuss threading issues, performance, usage, etc.;
Design a cache (ask lots of question!).

2nd guy (Senior SDE):

Chatting about experience and stuff (for about an hour)..
Implement an algorithm converting roman numbers to integers

3rd guy (hiring manager, Senior Developer Lead):

I had another meeting with him the day before this interview loop, it was more screening interview, and he asked me to implement an algorithm which finds whether two linked lists are merged and find a point of merge.
At another interview with him (in the interview loop day) he asked me following:

Serialize/deserialize tree – given a tree (random binary tree, not BST), you need to serialize it, transfer it to another place (lets say, another computer in the network), and restore it to its original state.
Design an autosuggest service (similar to the autocomplete on Google’s search page)

4th guy (Senior SDE):

WPF questions: difference between Windows Forms and WPF, MVVM-related questions, Commands, binding;
Task: I had to implement single writer multiple reader object (where readers can’t read if writing is in progress, and writer can’t write if there are readers reading); Solve writer starvation problem (when writer can’t write because there all lot of reader and they’re keep coming).

5th guy (Principal Program Manager):

BST tree traversal (easy one, but he asked to write down the solution on paper, weird..);
Memory manager: design and implement.

That’s it, 6+ hours total.

Little update on a “footwell lights” installation post

2011-05-27T22:49:00.000-07:00

Originally I installed a cathode under the driver’s seat by attaching it to the seat sprint underneath. Well, after some time went off, and when I took it off, it was broken. Turns out, if you install it this way, it will break eventually because you’ll be pushing on a fragile cathode with your weight . Anyway, install in on a rod, that goes under the seat. I reinstalled mine, and it works fine since then.

How do I – Android: Calculate MD5 hash from string

2011-01-31T16:21:00.001-08:00

There is a built-in MessageDigest class for hash calculation. It will calculate hash using specified algorithm.

/**              
 * Gets the hash value from the specified string.              
 *               
 * @param value              
 *            Target string value to get hash from.              
 * @return the hash from string.              
 */              
public final String getHashFromString(String value) {              
  if (value == null || value.length() == 0) {              
    return null;              
  }              
              
  try {              
    MessageDigest hashEngine = MessageDigest.getInstance("MD5");              
    hashEngine.update(value.getBytes("iso-8859-1"), 0, value.length());              
    return convertToHex(hashEngine.digest());              
  } catch (Exception e) {              
    return null;              
  }              
}              
              
/**              
 * Convert byte array to hex string.              
 *               
 * @param data              
 *            Target data array.              
 * @return Hex string.              
 */              
private static final String convertToHex(byte[] data) {              
  if (data == null || data.length == 0) {              
    return null;              
  }              
              
  final StringBuffer buffer = new StringBuffer();              
  for (int byteIndex = 0; byteIndex < data.length; byteIndex++) {              
    int halfbyte = (data[byteIndex] >>> 4) & 0x0F;              
    int two_halfs = 0;              
    do {              
      if ((0 <= halfbyte) && (halfbyte <= 9))              
        buffer.append((char) ('0' + halfbyte));              
      else              
        buffer.append((char) ('a' + (halfbyte - 10)));              
      halfbyte = data[byteIndex] & 0x0F;              
    } while (two_halfs++ < 1);              
  }              
              
  return buffer.toString();              
}

That’s it :). Have fun.

Java2html

Arduino

2011-01-07T11:01:00.001-08:00

Well, I decided to try it. Looks really cool from what I’ve seen so far. Starter kit shipped already from sparkfun.com. Can’t wait :)!

Mazda 6: Footwell and cupholder lights, and door sills installation

2010-12-15T17:17:00.001-08:00

First of all, disclaimer:

I’m not responsible for any damage you may cause to your car or, even worse, to yourself using instructions provided bellow. I’m not a professional mechanic and what not, so use this at your own risk. Read entire post first and be sure you understand everything before you start it. If you’re in doubt – ask mechanic to do installation for you.

So, today I’ll show you how I installed:

footwell lights
LEDs in cupholder
lighted door sills

These instructions are for Mazda 6i 2007 (Gen I) Sedan (they maybe applicable for other models of Gen I, but I can’t tell for sure). This is how it looks installed:

I will start with stuff you will need:

Major components – cold cathodes, LEDs, lighted door sills, tree-position switch.

You can get your cathodes here: http://www.oznium.com/ (amazing site with great customer service). You can get your LEDs there too, but I used another site for LEDs (and some other stuff): http://www.superbrightleds.com/ – this one, they have prewired LEDs, and housing for them, and lots of other cool stuff :). When it comes to door sills, you need to check eBay.

Cold Cathodes (Blue, 12”, with transformers);
Round Rocker Switch (three position, without LED);
Prewired LEDs (get housing for them too)
Door sills (this link may expire, so just look on eBay for best options/price)

Supplementary components (you might have them already :)):

Wire (red and black), 18 AWG (or 20 awg, but I used 18, and I got mine @ Radioshack);
Add-a-fuse connector;
Fuses (5A @ least).
Butt and female push-on connectors;
Heat shrinking tubes (for 18-20 awg wire, but I’d rather buy for variable size, because you’ll need some bigger ones);
JST 2 Pin connectors (male and female);
Multimiter;
Digital caliper;
Crimping tool;
Soldering stuff – soldering iron, solder, lead, etc;
1/4” and 3/4” hole bits;
Small files (round one, at least, you’ll need it to clean holes);
3M double-sided scotch (2 rolls :), you’ll use it to attach door sills);
12V power source (I made my from old laptop power connector);
Pliers;
Set of screwdrivers (flathead and Phillips);
Clamps (at least 10);

Step 0 – Measure wires

I forgot to do that, so you’ll need to do that yourself (I mean I forgot to write down those numbers).

Step 1 – Creating wiring harness

Start with cathode transformers.

Remember: You can not extend wires that go between cathode and transformer (in fact, you can, and there are extension wires for this, but its not recommended, because cathodes will dim, or may not work).

You’ll need ~5 feet of red/black wire (measure it by yourself). Solder your wires to respective transformer wires and cover with heat shrinking tubes.

Tip: If you don’t have heatgun, you can use your wife’s hairdryer :) (it works nice too).

Repeat this step for all four transformers, but for cathodes that will go under front seats use shorter wire.

Test your wires (connect cathodes and connect them all to 12V source). As a rule of thumb, test connections you’ve made often, to uncover problems before its easy to fix them, and when everything installed.

Now, add JST connector (male) to the transformer wire. I decided to go this way because it simplified installation (and you can replace transformer later simply unplugging it from harness).

That all for cathodes wiring preparation. Moving to the next step.

Step 2 – Install LEDs in cupholder (Requires drilling!)

OK, in this step you’ll need to drill 3 holes in cupholder: 1 for switch, and 2 for LEDs. If you don’t feel like drilling holes in your cupholder, well, you’ll need to find another place for switch and/or rework wiring diagram (comes later) for your needs.

Start with LEDs (and holes for them):

(LEDs on picture above is prewired and has a housing on it)

Cover places where you want your LEDs to be with some painting tape (it will reduce tear out).

Use 1/4” hole bit to drill holes in cup holder.

Since LED with housing is bigger than 1/4”, use a file to make hole a little bigger:

Now you can install LEDs in place and work on wiring. I soldered wires from both LEDs together and added a male JST connector at the end.

Use 3/4” hole bit to drill hole for rocker switch. Use a files to make hole a bit larger and add necessary notches (measure as you go).

Test your wires:

That’s all pre-wiring you’ll need for cup holder.

For door sills you don’t need any special wiring, just make sure they work.

By the way, my sills draw 80 mA of current (its important to know, because you’ll need to choose a fuse later):

Step 3 - Creating additional harness

You need a prewired add-a-fuse connector. See the pic below to get an idea how it should look:

(it has fuse in it)

Also, you’ll need these two connectors to connect to constant ground and variable (door) ground.

(Actually, pics a not up-to-date, and for the first pic you don’t need extra wire, and for the second one you’ll need ring connector for 12mm bolt).

And a final piece of the wiring harness – set of female connectors that you’ll plug your cathodes and cup holder LEDs into. Prewire 6 (one extra) female connectors, solder them together, and add some red/black wiring. I don’t remember how long that wire should be, but for red it should be enough to go from arm rest to driver side kick panel. And for the black – you need ~2 feet, from harness, to switch on a cup holder (and if you have your switch somewhere else, adjust wires appropriately).

Cover with heat shrinking tubes, and that all for this step.

Step 4 – Attaching door sills

Remove your plastic sills from a car, clean them up thoroughly. Add 3M double-sided tape on a plastic sill and add a lot of it on a metallic one. Use enough to level it with already attached 3M stripes (well, if yours come with 3M tape (but they usually do)).

(red – place where you need to add 3M tape, pic from http://home.online.no/~rekse/mazda6/gallery.htm).

Use clamps to hold sill in place, take your time.

Sill attached:

Before you start doing this for rear sills, you’ll need to bend them a little. Because they come straight, and plastic trill has some curved corners. Do it slowly and gently, take your time. It took me several hours in the evening to attach these (and I left them overnight with clamps).

Step 5 – Before you install.

Before you install, you need to choose a fuse for your new wiring you’re about to install in your car. Use your multimeter to check how much current it draws. Mine was 3+ Amp, so I took 5F fuse.

That’s all preparations you’ll need to do before you start installing it.

Step 6 – Installation (cathodes)

Before I start explaining how to install it in a car, here is a “wiring” diagram :)

As you can see, all cathodes are connected under arm rest. Power goes from fuse box, and they have 2 grounds, depending on switch position: constant ground (there is a bolt next to hand brake and variable ground, from doors). Sills has independent wiring (connected to fuse box and door ground, in one place).

Start installation by removing gear level cover (remember, cigarette lighter and lights are connected to it, so be careful. Use a small flathead screwdriver to unfasten cigarette lighter.

I recommend disconnecting your battery now (“-“ terminal).

Using 12 socket key remove nut displayed on pic below:

Attach following ground connector, and put nut back. This is your constant ground point.

Note: Clean up any rust under that nut, if you have any.

Start installing cathodes. Remove following two screws, that holds center panels in place, that will give you more freedom (those screws are covered with some caps, see pic below).

Install wiring harness. Make sure you have left enough wire under arm rest and there are enough wire to reach fuze box (red/black wire with white electric tape on it, electric tape is not required, but it tells me what wire is that).

Remove the glove box (its pretty easy, see my other post for details :)):

Attach cathode:

Connect cathode to the transformer. Attach transformer to “frame beam” (I don’t know what’s the name of that part, but you can get an idea from images below):

Run wires behind panels to the compartment under arm rest. Do same stuff for driver side cathode. I found a good place for cathode itself next to OBDII port.

Clean up driver side wiring (use cable ties to secure wires):

Next, install cathodes (and transformers) under passenger and driver seats. I attached cathodes as well as transformers directly to springs under the seats and run wire to the center console, under the arm rest, where all wires go. Make sure you run wires under the seat track, so you can move your seats and don’t run over wires and damage them.

Now, connect everything :)!

Look scary :). Now, cleanup! (Always secure wire, don’t left them hanging!).

Connect grounds to the switch and install cup holders in place (yellow/center connector goes to harness, left and right – “always on” and “on when map lights on”, or vice versa, depending on how you attach them):

And final touch for cathodes – pluging them to fuse box. You need constant 12V+, and you can use map light for that. Use your manual to locate correct map light fuse, remove it, insert into “add-a-fuse” connector, next to 5A fuse (it should be left most, and 5A right most), and insert “add-a-fuse” instead of fuse you removed. Connect power wire you run from harness to kick panel, secure everything in place:

That’s almost everything for cathodes. But now you can hook up your battery and test everything (put your switch to “always on”/constant ground position). Your cathodes and cup holder LEDs should work now.

I’ll explain how to connect to variable ground in next step (along with door sills installation).

Step 7 – Installation (sills)

Start by locating ground wire. For instance mine was yellow-black. How did I find it? I removed door courtesy light cover, bulb (LED, I installed recently :)), screw next to bulb socket. Then I inserted multimeter to find out which one is negative:

Then I looked to what wires its connected:

And this gave me yellow-black.

Now, you can install sills wiring, or simply connect variable ground from cathodes. Anyways, I cut the wires, and connected to it: cathodes ground, driver side sills connector, and next piece of wire that will go to driver side back seat.

Secure wires, attach sill and run wires to the back seat. Couple words about power: you need to attach to the same “add-a-fuse” connector, you’ve attached your cathodes to (check back the wiring preparation step, I made “V” connection for add-a-fuse, so both cathodes and sills wiring could same 12V+ source).

For the back seat installation you need to remove back seat first. There two locks under the seat, pull them and release the connector. Don’t forget to unfasten center seat belt :).

Connect door sill, and run wire to passenger side. There is a wiring goes under the seat, so you can use same route for your wiring:

Connect sills on passenger rear and then front sides. This is how connector should look like when everything is secured:

Install sills, clean up all the mess, connect your battery and enjoy!

Android Gingerbread is out!

2010-12-09T09:38:00.001-08:00

A lot of improvements and some new nice features. Go here and find out more.

Awesome Android t-shirt

2010-11-06T13:13:00.001-07:00

Do you want an awesome Android t-shirt? Go here and grab one!

Microsoft Interviews, again

2010-10-24T12:23:00.001-07:00

I had series of interviews here at Microsoft, for SDEII positions. I don’t know results yet, but I think I can share some questions I was asked:

1. Design and code algorithm that determines whether liked list is cycled.
2. Given an array of strings, print all groups of anagrams in array (like Group 1: “abc, cba”, Group 2: “demo, mode”).
3. Reverse linked list. For instance, given linked list "A –> B –> C –> D”, you’ll need to get “D –> C –> B –> A”. Design, analyze algorithm and code.
4. Print all possible paths in matrix, from lower left corner to upper right. Design, analyze and code algorithm.
5. Design elevators management system (1 building, 6 elevators).
6. You have 100 storey building and 2 marbles. You need to find a floor when marbles being thrown from the floor will break in a least number of measurements.
7. You have a matrix m x n. It contains numbers sorted in ascending order by rows and by columns. You need to find a most efficient algorithm to find a number in that matrix.

Enjoy.

How do I – Android: Check current SDK version in application

2010-10-06T13:41:00.001-07:00

Its never been easier to check current SDK version your device is running on. Use

Build.VERSION.SDK_INT

it contains value from Build.VERSION_CODES enumeration. For instance, following code determines whether current version is Froyo or higher:

/**
* Checks if SDK device is running on is Froyo or higher.
*
* @return True, if SDK device is running on is Froyo or higher; otherwise false.
*/
public boolean isSdkFroyoOrHigher() {
return Build.VERSION.SDK_INT >= Build.VERSION_CODES.FROYO;
}

How do I – Android: Check if SD card is present

2010-10-06T12:54:00.001-07:00

Sometimes its necessary to know whether device has SD card present (mounted), before start doing any operation(s) with it. So, here is some simple way to determine is SD card mounted:

/**
* Checks if SD card is mounted.
*
* @return True, if SD card is mounted.
*/
public boolean isSDCardMounted() {
return android.os.Environment.getExternalStorageState().equals(
android.os.Environment.MEDIA_MOUNTED);
}

That’s it, if its mounted, you’ll get true, otherwise false.

How do I – Android: Unmount SD card

2010-10-06T11:39:00.001-07:00

Simple question, but sometimes people don’t know how to do this. So, in order to unmount SD card on Android do the following:

Open “Settings”
Go to “SD card & phone storage”
Press “Unmount SD card”

This is all you need to do :)

Light show in Kharkov, Ukraine

2010-09-22T09:22:00.001-07:00

Have you seen this? No, then check this out!

How to install XCarLink iPod/iPhone adapter [ Mazda 6 ]

2010-07-21T09:42:00.001-07:00

Note: This will not work, if you have a satellite radio, or any other device that uses aux port on your stereo.

Ok, I installed this kit couple weeks ago, but finally found a time to write about it. So, first things first – a kit itself:

[ Package content ]

[ Bluetooth harness, iPod/iPhone connector, XCarLink module ]

Next, tools you’ll need:

Ratchet wrench, extension, and 10 socket;
Phillips screwdriver;
Small flathead screwdriver;
Some cable ties;
Electric tape (optional, but highly suggested);
Pliers;
Bicycle wheel mounting tool (I don’t know whether its called like this, and you may not need this, but I found it useful);
Scissors;
Light;
And, maybe, some cloth.

OK, lets get it done.

Put your car on a brake. And start with removing cupholder and gear shift panel. You don’t need any tools to remove it, just pull it up and will pop right away. Be careful, do not break clips that hold it in place, just don’t put to much force in it.

Do not remove shift panel just yet. Start your car and put it into reverse gear (“R”), if you have ATX (as I do). Unscrew the shift knob.

Stop the car, and disconnect negative (black wire) from battery (its better be safe than sorry).

Now, easily remove shift panel. Remember that you have two wires underneath – cigarette lighter and illumination for shift panel. Turn over this panel and you will see it.

To remove illumination harness, grab that plastic piece near the wire and turn it, this way you release a bulb and pull it (do it for both).

To unplug a cigarette lighter, use a small flathead screwdriver, find a clip that holds it and gently press on it and pull it at the same time.

When you’re done, give them a good cleaning.

So, now it should look like this:

Then, remove the liner from the armrest compartment. You can see a vent (?) holes on the bottom, I put iPod connection wire thru this holes.

Now its time to remove center console.

Note: Center console secured with two screws at the front and one bolt on right (behind the glove box). Do not forget about that bolt!

To find out how to remove glove box read my earlier post here.

Bolt:

Note: Be careful not to drop that bolt (as I did). I was lucky that it fell where I was able to reach it with some long pliers.

Start removing the console. I wasted a lot of time doing it (everybody says its easy, but for me it wasn’t). Start pulling from the top. Then from the bottom. Use a tire mounting tool, that I’ve mentioned before that. Insert that tool into the holes and press the clips inside, pulling console at the same time (take your time).

Note: Do not use anything sharp, metal around console, because you can end up scratching/damaging console cover.

Now put some cloth on gear-change shift lever, pull of the console and lean it against the lever (don’t try to remove completely, you don’t need to do this extra work, besides its not that easy :)).

Now, connect XCarLink module to the aux port.

Its up to you how you will run the wires, but here’s what I did.

Remove plastic cover that hides a bolt on your driver’s side center panel cover. And run the wires behind this panel. If you have a Bluetooth kit, don’t put that screw back just yet, Bluetooth wire will go behind that panel too.

Now, couple notes about installing Bluetooth. I decided that I want a Bluetooth mic to be on a driver side front pillar. Mount mic on a pillar and run wires from it under the steering wheel and behind that drivers side. Secure it underneath with cable ties (use pliers to remove excessive ties).

I don’t have pics how I did it. But schematically it looks like this (orange – bluetooth harness):

Its time to run wire for iPod connector. Open armrest compartment, use pliers to cut a hole big enough to put a cable thru it. Run a wire thru the hole. Take a scissors and cut a small hole in liner, put a wire thru it and then thru the hole in compartment. Measure the right amount of cable that you want to be available in compartment, rest should go inside the center console.

Ok, when you’re done with wires, its time to connect everything together and test. Connect all cables to module, put back battery and try it :). Enjoy the sound and ask your friend/family member call you, so you can test bluetooth.

So, its time to put everything in place/together. Don’t forget to secure all wires/module inside the console.

Photos below show where I put my XCarLink module (you can use another place, but for me that one worked best). New wires with orange tape on it.

Steps to put everything back:

Install center console (make sure its secured);
Check all climate control knobs, there is a big chance that you can mess with temperature control wire. If you can not turn that knob left completely, it means you “broke” it. Put console back and start turning back and forth that knob slightly. Look inside, where that bolt that suppose to hold console is. You will see a moving wire (that moves a lever). Loose that wire from a clip that holds it. Rotate knob on left completely, and than put pack wire inside a clip.
Put back bolt;
Put back 2 screws;
Install glove box;
Connect cigarette lighter and two bulb from shifter panel;
Secure shifter panel;
Secure cupholder;
Clean up all the mess :).

And.. you’re done. Congrats, and happy DIY’ing.. :).

LEDs…

2010-07-07T15:05:00.001-07:00

Just ordered some LEDs for Mazda interior.. will see how it will come off.
PS: Ordered from http://www.superbrightleds.com/.

Changing cabin air filter [ Mazda 6 ]

2010-07-07T15:02:00.001-07:00

Now, I want to show you how easy is to change cabin air filter.

Tools / materials you’ll need:
- new cabin air filter;
- hands.

First thing first, your air filter is behind glove box. So, first thing to do is to remove glove box:

The easiest I found to do that is to unfasten that rope that you see on image above. When that done, you can remove glove box (it holds by to hinges). Press slightly at the top of the glove box and bend it and pull it. It will come off easily :). Be careful, as soon as you pull it off, it will just fall down.

[ Removed glove box ]

Now, locate the air filter box. Grab little handles at the bottom and pull them gently, this way you’ll remove air filter housing cover.

[ Cover ]

Remove old filter and put your brand new one :).

[ Old filter in place ]

[ Brand new filter from NAPA… ]

And, put everything back in reverse order: cover, glove box and fasten back the glove box “holder”.

And.. one scary picture of my old air filter :)

Have fun and happy DIY.

15$ Discount on XCarLink from RPM Store

2010-06-29T15:31:00.001-07:00

If you’re planning to buy an iPod/iPhone integration kit for your Mazda 6 from RPM Store, use this coupon code to get a 15$ off :)

Code: 6CLUBMP3

Found on Mazda6Club Forum.

Thanks to RPM guys, will see how it goes.

IE9 is on its way

2010-06-23T23:02:00.001-07:00

IE9 is on its way and you can try a preview here - http://ie.microsoft.com/testdrive/. Check out the link, a lot of nice samples of HTML 5 :).

How do I – Android: create a ListView control

2010-05-21T20:58:00.001-07:00

Android has a nice control to display data as list called ListView. It’s very easy to use. First of all, put a <ListView /> on form (in your markup xml). Then, attach adapter, that will provide data for your list view, in code, hook up click (and long click) listeners, and that’s it. Unless you need something fancy (which you can definitely do :)). Check out the example below.

1. Declaring list view in xml markup:

File: main.xml

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android=http://schemas.android.com/apk/res/android
    android:orientation="vertical"
    android:layout_width="fill_parent"
    android:layout_height="fill_parent">
      <ListView
            android:id="@+id/demoList"
            android:layout_width="fill_parent"
            android:layout_height="fill_parent"
            android:background="#FFFFFFFF">
      </ListView>
</LinearLayout>

2. Declaring a list view item – I’m going to use a ArrayAdapter to populate listbox and it requires a TextView resource to be specified as one of the .ctor parameters:

File: list_item.xml

<?xml version="1.0" encoding="utf-8"?>
<TextView
      xmlns:android=http://schemas.android.com/apk/res/android”
      android:id="@+id/itemText"
      android:layout_width="fill_parent"
      android:layout_height="wrap_content"
      android:padding="10px">
</TextView>

Please notice that this TextView element was declared in separate file – list_item.xml.

3. Hook up your list view in code:

package org.example.demo;

import android.app.*;
import android.os.*;
import android.view.*;
import android.view.ContextMenu.*;
import android.widget.*;
import android.widget.AdapterView.*;

public class Demo extends Activity implements OnItemClickListener {
      private final String[] monthList = new String[]
            { "January", "February", "March", "April", "May",
              "June", "July", "August", "September",
              "October", "November", "December" };

      @Override
      public void onCreate(Bundle savedInstanceState) {
            super.onCreate(savedInstanceState);
            setContentView(R.layout.main);

            // Initialize list.
            ListView list = (ListView) this.findViewById(R.id.demoList);
            list.setOnCreateContextMenuListener(this);
            list.setOnItemClickListener(this);
            list.setAdapter(new ArrayAdapter<String>(this,
                R.layout.list_item, monthList));
      }

      @Override
      public void onItemClick(AdapterView<?> arg0, View arg1, int arg2, long arg3) {
            // Handle list clicks.
      }

      @Override
      public void onCreateContextMenu(ContextMenu menu, View v,
          ContextMenuInfo menuInfo) {
            // Create context menu.
      }
}

One comment about code: please notice that how we referenced item template – R.layout.list_item!

You can find more information about ListView and Adapter in Adroid Documentation.

Cheers!

How do I – Android: launch another activity (from my project)?

2010-05-09T22:48:00.001-07:00

You use intents to start an activity. Intent describes what exactly you want to do.

I you want to launch an Activity within your project you need to do the following:

1. Lets say you have an Activity “MainActivity.java” with button and “Second.java” – second activity that you want to show when user presses on a button.

2. Define a new intent passing current context (your current activity is an inheritor of a Context) and your target activity’s class name (Second.class in this case).

3. Call startActivity method passing an instance of the Intent created before:

private void onShowViewClick() {
Intent newActivityIntent = new Intent(this, Second.class);
this.startActivity(newActivityIntent);
}

Now, when you click on a button – a new activity will be started.

NOTE:
Don’t forget to declare your activity in AndroidManifest.xml.

How do I – Android: create a new activity?

2010-05-09T21:40:00.001-07:00

Only a very simple applications consist of one form (activity). To create new activity in Android (Eclipse) follow these steps:

1. Open your project in Eclipse
2. Expand your project folder structure down to the “layout” folder and call a context menu on this folder:

3. Select “New” –> “Android XML File” from context menu:

4. Once you click this menu item a new Android XML file dialog will be opened where you will need to fill at least “File” field, all other fields are optional.

Press “Finish” and you will get a new activity in your Android project.

Well, now when you have your layout defined, you need to create a class representing this activity (it is not necessary in some cases)..

To create a new class that will be used to show your activity just defined on screen you need to:

1. Select “File” –> “New” –> “Class…”
2. Specify source folder and package name – by default that will be “src” folder under your project tree;
3. Provide name for you class – its better to give your class name same as you gave your layout file (for instance, if your layout name is “aboutform.xml”, than name your class “aboutform.java”);
4. Specify superclass – the one that you want to inherit from – it must be android.app.Activity);

5. Press “Finish…”

Now, when you have your class and layout – you need to “connect” layout and class. You can do that by specifying which layout your activity must use in onCreate method of your activity.

1. Override onCreate method, put the following code in your activity class:

import android.app.Activity;
import android.os.Bundle;

public class Second extends Activity {
      @Override
      public void onCreate(Bundle savedInstanceState) {
            super.onCreate(savedInstanceState);
            // ...
      }
}

Read more about activity lifetime here!

A sidenote: when you create a new layout an Eclipse automatically regenerates a resources and puts a new resource identifier in R class (can be found in “gen” folder under your project tree). For instance, you’ve added a new layout with name “second".xml”, it means that when R file will gets regenerated you will see a new resource R.layout.second and it will be available from your code (as your layout identifier).

2. To specify which layout must be displayed use setContentView method and specify target layout Id:

this.setContentView(R.layout.second);

Final version should look like the following:

import android.app.Activity;
import android.os.Bundle;

That’s all, you can use your activity.

How do I – Android: create a new project?

2010-05-09T21:18:00.001-07:00

To create a new Android project in Eclipse do the following: click “File” –> “Android Project”.

You will get following window:

Fill out the following fields:

Project name – your project name;
Build target – select one of the build target that you want to use (if you need some Google-specific features, like maps, select “Google APIs”, it will include all Android features plus some additional functionality);
Package name – your package name (it must consist at least from two parts – something like “orgname.projname”);
Create Activity (checkbox and field) – Check this checkbox if you need an activity to be created along with project; If you need new activity – provide a target activity’s name, otherwise uncheck this checkbox;
Min SDK Version – minimum required Android SDK version.

Press Finish (or Next if you need a test project) and that’s it!

How do I – Java: get current date/time in UTC format

2010-05-04T16:21:00.001-07:00

To get date/time in UTC format you’ll need two classes java.text.SimpleDateFormat and java.util.TimeZone.

Create an instance of the SimpleDateFormat passing a desired format and set a time zone for it (by calling TimeZone.getTimeZone with “UTC” value).

Example:

SimpleDateFormat formatUTC = new SimpleDateFormat("yyyy-MMM-dd HH:mm:ssZ");

formatUTC.setTimeZone(TimeZone.getTimeZone("UTC"));

return formatUTC.format(new Date());

Note: Using “GMT” time zone you can get time in GMT format.

How do I – Eclipse: generate getter/setter for class fields

2010-05-04T14:09:00.001-07:00

Its a good practice to keep your class fields private. But declaring getter/setter for each field may be a time consuming (and boring) operation, for instance, if you have more than 3 private class fields.

But, Eclipse has a nice helper mechanism of generating getters/setters automatically from your class fields.

Lets say we have class Animal with 4 fields and we want to generate getters (and setters) for them:

import android.graphics.Color;

public class Animal {

private int age;

private String kind;

private int weight;

private Color color;

}

Open context menu and select “Source” –> “Generate Getters and Setters…”.

You will get the following dialog:

Configure your fields and press OK and you will get your getters/setters generated for you.

Happy Eclipse’ing

How do I – Eclipse: Expand/collapse all methods

2010-05-04T11:56:00.001-07:00

To expand or collapse all methods Eclipse has following keyboard shortcuts:

Collapse All - Ctrl+Shift+/

Expand All - Ctrl+Shift+*

Happy Eclipse’ing..

How do I – Eclipse: Create a user spell checking dictionary

2010-05-03T16:07:00.001-07:00

You know that Eclipse has built in spell checker, but what if you want to add some very specific words to spellchecker (and you want them to be treated as valid words).

For example, I want “Javadoc” keyword, that appears in comment , to be a valid word for Eclipse (I know what “Javadoc” means and I don’t want it to be underlined with red):

Solution – create a user dictionary.

First of all, create a .txt file somewhere on file system, then go to “Window” –> “Preferences”. An then: “General” –> “Editors” –> “Text Editors” –> “Spelling” and specify the full path to the file just has been created in “User Defined Dictionary” field.

Press “OK” and you’re done. Now you can add words to your custom dictionary.

Move your mouse over the word with spelling warning and you’ll see the following:

Select “Add {your_word} to dictionary” and … that’s it!

Happy Eclipse’ing :)

How do I – Eclipse: Find all references

2010-04-30T11:17:00.001-07:00

If you are familiar with Visual Studio, you know that you can find references pretty easy there. And, if by any chance you are the lucky owner of ReSharper (http://www.jetbrains.com/resharper/) – the great plugin for Visual Studio, its even easier.

How about Eclipse? Well, it’s easy too, just select variable and in context menu select “References” and then “Workspace”, “Project” or “Hierarchy”. That’s it :).

Happy Eclipse’ing :)

How do I – Eclipse: Enable line numbers in editor

2010-04-30T10:52:00.001-07:00

I really got used to line numbering in Visual Studio. It was the first thing I did after installing VS. Now, when I moved to Eclipse, I need those numbers in Eclipse too :).

So, how can you enable line numbers in Eclipse? Go to Window menu, then Preferences –> General –> Editors –> Text Editors and check “Show Line Numbers” there. Press “OK” and that’s it.

Note: Eclipse Version – Eclipse IDE for Java Developers (Galileo).

Happy Eclipse’ing :)

Algorithms: What are the differences between array and linked list?

2009-03-30T08:43:00.000-07:00

Итак, в чем же разница между массивом и односвязным списком?

Space:

1. В случае массивов, для хранения 10 элементов нам потребуется 10 * sizeof(element) байт памяти.
2. А в случае со односвязным списком, нам понадобится 10 * (sizeof(element) + sizeof(pointer)) места.

Следовательно, нам понадобится больше места/памяти в случае списка (по сравнению с массивом).

Time:

Т. к. массив предоставляет возможнось доступа к элементу по индексу, то в случае массива время доступа к произвольному элементу будет O(1), в то время как поиск элемента в списке потребует O(n) времени.

НО:

1. Некоторые структуры данных удобней представлять в виде именно связных списков, а не массивов.
2. Удаление и добавление новых элементов проще производить в списках, чем в массивах (массивы не расширяемы).
3. В случае массивов нет фрагментации памяти (т.к. элементы массива следуют друг за другом в памяти), как это может быть со связным списком.

Algorithms: Find string combinations

2009-03-30T08:19:00.000-07:00

Задача: найти все комбинации заданой строки.

Эта задача очень близка задаче поиска всех возможных перестановок строки. Пожалуй, если вы не знакомы с алгоритмом поиска возможных перестановок строки, то я бы советовал для начала ознакомится с ним.

Для начала в двух словах раскажу что такое комбинации в строке. Рассмотрим строку "abcd". В этой строке, например, две пары "ab" и "bc" являются комбинациями, в то время как "ab" и "ba" - нет.

Запишем теперь возможные комбинации для слова "abcd":

a	b	c	d
ab	bc	cd
abc	bcd
abcd	bd
abd
ac
acd
ad

В таблице выше представлены все возможные комбинации слова "abcd".

Итак, что мы можем получить из такого представления? А мы можем получить собственно сам алгоритм генерации комбинаций. Рассмотрим, к примеру, колонку "c" - как мы можем получить все комбинации для "c" - очень просто, берем "c", это будет одна комбинация, затем поочередно прибавляем значения со всех колонок справа. Получаем: "c" и "cd". Далее, расмотрим "b" - для "b" действует то же правило, берем "b", а затем к символу "b" прибавляем все значения из колонок справа... и так далее.

Следовательно, мы приходим к следующему рекурсивному алгоритму:

Для каждого символа во входящей строке, начиная со стартовой позиции и до конца
Выбираем символ из входящей строки в результирующую
Печатаем комбинацию
Если текущий символ во входящей строке
Переходим на следующий цикл рекурсии, начиная при этом с символа, следующим за текущим символом.

Приведу реализацию этого алгоритма на C# (и я думаю сразу "все станет на свои места"):

    1 /// <summary>
    2 /// Print string combinations.
    3 /// </summary>
    4 /// <param name="inputChars">Input string characters.</param>
    5 public static void PrintCombinations(char[] inputChars)
    6 {
    7     char[] outChars = new char[inputChars.Length];
    8     DoPrintCombinations(inputChars, outChars, 0, 0);
    9 }
   10 
   11 private static void DoPrintCombinations(char[] inputChars, char[] outChars, int level, int start)
   12 {
   13     for (int index = start; index < inputChars.Length; index++)
   14     {
   15         outChars[level] = inputChars[index];
   16         outChars.PrintArray();
   17         if (index < inputChars.Length - 1)
   18         {
   19             DoPrintCombinations(inputChars, outChars, level + 1, index + 1);
   20             outChars[level + 1] = '\0';
   21         }
   22     }
   23 }
Напомню, что PrintArray - это extension-метод, который мы ввели для облегчения вывода массивов на консоль.
 
Пример:

    1 public static void Main()
    2 {
    3     CommonAlgorithms.PrintCombinations("abcd".ToCharArray());
    4 }
 
Результатом работы этой програмки приведен ниже:
 
 
В следующий раз раскажу о поиске всех перестановок (хотя об этом надо было расказать сначала :))..
 
Happy coding...

Крымские виды (панорама)

2009-03-29T04:26:00.000-07:00

Давненько это было. Снято еще "стареньким" Olympus 570 UZ (точно уже и не помню). Снял давно, и вот только сейчас дошли руки сделать панорамки.

Algorithms: Check whether two words are anagrams

2009-03-23T15:03:00.001-07:00

Задача: необходимо проверить, являются ли два слова анаграммами.

Для начала давайте вспомним (или узнаем) что такое анаграммы. Итак:

"Анаграмма - литературный приём, состоящий в рекомбинации букв или звуков определённого слова (или нескольких)" или более простой вариант определения "Анаграмма -это перестановка букв, посредством которой из одного слова можно составить другое" (более подробно можно почитать в Википедии).

Итак, есть много (и довольно разных) вариантов решения этой задачи. Раскажу об одном из них. Итак, для начал предположим что у нас слова, которые мы будем сравнивать - находятся в кодировке ASCII. Далее, оба слова необходимо перевести в нижний регистр (для этого можно использовать String.ToLower() ну или придумать свою замену, если посчитаете, что ToLower() может отнимать много времени).

После того как оба слова переведены, можно для первого слова построить "гистограмму" вхождения буквы в слово. Например, у нас есть слово "streaming", следовательно гистограмма для это слова будет выглядеть как

s - 1
t - 1
r - 1
e - 1
a - 1
m - 1
i - 1
n - 1
g - 1

Далее, анализируя второе слово, мы можем уменьшать значения в гистограмме. И на последнем шаге необходимо пробежатся по всем значениям в "гистограмме" и проверить все ли значения равны 0. Если нет - то сравниваемые два слова не анаграммы.

Приведу пример реализации этого алгоритма на C#:

    1 /// <summary>
    2 /// Check whether two words are anagrams.
    3 /// </summary>
    4 /// <param name="value1">First word.</param>
    5 /// <param name="value2">Second word.</param>
    6 /// <returns>True if two specified word are anagrams, otherwise false.</returns>
    7 public static Boolean IsAnagram(String value1, String value2)
    8 {
    9     if (String.IsNullOrEmpty(value1) || String.IsNullOrEmpty(value2) ||
   10         value1.Length != value2.Length)
   11     {
   12         return false;
   13     }
   14 
   15     // convert strings to lowercase.
   16     value1 = value1.ToLower();
   17     value2 = value2.ToLower();
   18 
   19     int[] histogram = new int[256];
   20 
   21     for (int index = 0; index < value1.Length; index++)
   22     {
   23         histogram[value1[index] - 'a']++;
   24     }
   25 
   26     for (int index = 0; index < value2.Length; index++)
   27     {
   28         int charIndex = value2[index] - 'a';
   29         if (histogram[charIndex] == 0)
   30         {
   31             return false;
   32         }
   33 
   34         histogram[charIndex]--;
   35     }
   36 
   37     return true;
   38 }
 
Сложность - O(n). 
 
PS: В следующий раз я раскажу как найти все комбинации (не путайте с перестановками) строки. 
 
Happy coding...

Algorithms: Romanian numbers

2009-03-23T13:49:00.000-07:00

Задача: необходимо преобразовать число, представленное в римской системе счисления в число в десятичной системе счисления (ну вдруг кто не знает или забыл как это "римские цифры" - то тогда здесь).

Алгоритм решения этой задачи довольно простой. Итак, необходимо двигатся с конца строки, увеличивая или уменьшая результат.

Итак, для начала построим "карту" соответствия римских и арабских чисел:

C	100
D	500
I	1
L	50
M	1000
V	5
X	10

А теперь, на примере можно рассмотреть собственно сам алгоритм. Возьмем к примеру число XIV (т.е 14). И, как я уже упоминал, необходимо двигатся в конца строки. Возьмем первый символ - "V". Ему, в "карте" соответствует число 5. Запоминаем это число как текущий результат и сдвигаемся дальше влево на один символ. Далее у нас символ "I" - ему соответствует 1 в "карте". Необходимо вычесть 1 с уже имеющегося результата - 5. Из этого следует, что если текущее значение меньше предыдущего, то необходимо от результата отнять текущее значение, иначе - прибавить. Итак, 5 - 1 получаем 4 и двигаемся дальше. Дальше у нас "X" - и соответствующее ему число 10. Так как на предыдущем шаге у нас была 1, которая меньше 10, то полученную 10-ку надо прибавить к результату. В итоге получем - 14.

И реализация на C#:

    1 /// <summary>
    2 /// Convert Romanian number to Arabic.
    3 /// </summary>
    4 /// <param name="value">Value to be converted.</param>
    5 /// <returns>Converted value if successful, otherwise 0.</returns>
    6 public static Int32 RomanToInt32(String value)
    7 {
    8     // Validate input parameters.
    9     if (String.IsNullOrEmpty(value))
   10     {
   11         throw new ArgumentNullException("value");
   12     }
   13 
   14     // Update string.
   15     value = value.Trim().ToUpper();
   16 
   17     var romanDigitDictionary = new Dictionary<String, Int32>
   18     {
   19         {"C", 100}, {"D", 500}, {"I", 1}, {"L", 50}, {"M", 1000}, {"V", 5}, {"X", 10}
   20     };
   21 
   22     // Validate string.
   23     for (Int32 charIndex = 0; charIndex < value.Length; charIndex++)
   24     {
   25         if (!romanDigitDictionary.ContainsKey(value[charIndex].ToString()))
   26         {
   27             throw new InvalidOperationException("String contains invalid characters");
   28         }
   29     }
   30 
   31     // Start conversion.
   32     Int32 result = 0;
   33     Int32 lastValue = 0;
   34 
   35     for (Int32 charIndex = value.Length - 1; charIndex >= 0; charIndex--)
   36     {
   37         Int32 currentValue;
   38         if (!romanDigitDictionary.TryGetValue(
   39             value[charIndex].ToString(), 
   40             out currentValue))
   41         {
   42             throw new InvalidOperationException();
   43         }
   44 
   45         if (currentValue < lastValue)
   46         {
   47             result -= currentValue;
   48         }
   49         else
   50         {
   51             result += currentValue;
   52             lastValue = currentValue;
   53         }
   54     }
   55 
   56     return result;
   57 }
 
Сложность такого алгоритма - O(n).
 
PS: В следующий раз я  раскажу как проверить являются ли два слова анаграммами.
 
Happy coding...

Високосный год и JavaScript

2009-03-22T05:40:00.001-07:00

Иногда возникает необходимость определить, является ли введенный/выбранный (например, из списка) пользователем год високосным.
В C# все просто:
bool isLeap = DateTime.IsLeapYear(1996);

Но, в JavaScript такого нет, к сожалению. Но вискосный год или нет, можно определить, используя следующую функцию:

Анализируя функцию, возникает вопрос: а не проще ли сделать year%4 == 0 и получить високосный год. Ответ: нет. Алгоритм вычисления высокосного года немного сложнее (поблагодарим Папу Георгия ХIII). Год считается високосным только в том случае если он делится на 4 без остатка (это мы знаем со школы), но при этом не делится на 100 без остатка, или, если делится на 100, должен делится и на 400 без остатка.

Happy coding...

Проблема при установке SQL Server 2005 на машину с AMD Phenom 8450 Triple-Core

2009-03-22T05:02:00.001-07:00

Хочу немного рассказать о проблеме, с которой я столкнулся при установке SQL Server 2005 на компьютер с AMD Phenom 8450 Triple-Core. Выяснения в чем дело заняли у меня почти целый день (к сожалению, у меня не было интернета под рукой, поэтому «погуглить» я не мог).

Итак, при установке сервиса SQL Server инсталлер пытался запускать службу, которая без видимых причин падала со следующей ошибкой:

An unhandled win32 exception occurred in sqlservr.exe [1456]. Just-In-Time debugging this exception failed with the following error: No such interface supported

Check the documentation index for 'Just-in-time debugging, errors' for more information.

For more information, see Help and Support Center at http://go.microsoft.com/fwlink/events.asp.

После долгих поисков (хорошо, что установка шла на новую систему, и я успел поэкспериментировать и с Windows XP, как с сервиспаками так и без, и с Windows 2003), наконец-то я выяснил J, что проблема (по части) «в железе».

Итак, способ лечения:

С командной строки запустить msconfig
Перейти на закладку BOOT.INI и нажать там кнопку Advanced Options…
В появившемся окне отметить опцию /NUMPROC= и выбрать значение кратное 2-м:
Сохраняем изменения. Перезагружаем компьютер.
Устанавливаем SQL Server 2005 и Service Pack 2 (обязательно!).
После установки Service Pack 2 необходимо проделать пункты 1-3 еще раз, но при этом в окне BOOT.INI Advanced Options снять флажок /NUMPROC= (вернув при этом 3 ядра «в строй»).

Hope this helps…

Algorithms: Convert string to integer

2009-03-22T04:56:00.001-07:00

Задача: необходимо преобразовать строку в число.

Для начала предположим, что строка у нас находится в кодировке ASCII. Наиболее очевидным и простым решением является проход строки справа налево.

Давайте на примере рассмотрим решение задачи. Итак, у нас есть строка "437". Двигаясь слева направо, мы на первом шаге берем символ "4". Как мы можем перевести "4" в соответствующее число: 4? Так как у нас строка в ASCII кодировке, мы можем взять '4' - у которого числовое представление 52 и вычесть 48, т.е. числовое представление '0'.

Примечание: более подробную информацию по кодировке ASCII можно найти здесь: American Standard Code for Information Interchange (ASCII).

Далее, получив второй символ "3" нам необходимо умножить предыдущее число 4 на 10 и найти числовое представление символа "3". После этого результат складываем и запоминаем: 4 * 10 + 3. На следующем шаге получим (4 * 10 + 3) * 10 + 7.

Этот алгорим можно представить как:

Start number at 0
If the first character is '-'
    Set the negative flag
    Start scanning with the next character
For each character in the string
    Multiply number by 10
    Add (digit character - '0') to number
Return number

И реализация на C#:

    1 /// <summary>
    2 /// Converts string to integer.
    3 /// </summary>
    4 /// <param name="input">Input string.</param>
    5 /// <returns>Resulting integer value.</returns>
    6 public static Int32 StringToInt32(String input)
    7 {
    8     // Validate input parameter.
    9     if (String.IsNullOrEmpty(input))
   10     {
   11         throw new ArgumentNullException("input");
   12     }
   13 
   14     Int32 position = 0;
   15     Boolean isNegative = false;
   16     Int32 result = 0;
   17 
   18     if (input.Length == 1 && !char.IsDigit(input[position]))
   19     {
   20         throw new InvalidOperationException();
   21     }
   22 
   23     // Validate whether input string starts with "-".
   24     if (input[position] == '-')
   25     {
   26         isNegative = true;
   27         position = 1;
   28     }
   29 
   30     while (position < input.Length)
   31     {
   32         if (!char.IsDigit(input[position]))
   33         {
   34             throw new InvalidOperationException();
   35         }
   36 
   37         result *= 10;
   38         result += (input[position] - '0');
   39 
   40         position++;
   41     }
   42 
   43     if (isNegative)
   44     {
   45         result *= -1;
   46     }
   47 
   48     return result;
   49 }

Сложность такого алгоримта - O(n).

PS: В следующий раз я покажу как перевести число из римской системы счисления в арабскую: XXI -> 21.

Happy coding...

Algorithms: Convert Integer to string

2009-03-22T03:59:00.000-07:00

Задача: перевести число в строку.

Возможно несколько вариантов рещения этой задачи.
Первый вариант - идем слева направо. Например, у нас есть число -123. Во-первых, мы во всех вариантах должны сначал проверить является ли число отрицательным, и перевести его в положительное (при этом запомнив, что изначально оно отрицательное). Далее, как мы можем получить число "1" из 123? Следующим образом:

123 / 100 = 1; 123 - 1 * 100 = 23 - первое число
23 / 10 = 2; 23 - 2 * 10 = 3 - второе число
3 / 1 = 3; 3 - 3 * 1 = 0 - третье число

Второй вариант предполагает проход числа справа налево. При этом как мы можем получить самое последнее число? Получив остаток от деления на 10: 123 / 10 = 3;

Алгоритм решения этой задачи приведен ниже:

If number less than zero
Multiply number by -1
Set negative flag
While number not equal to 0
Add '0' to number % 10 and write this to temp buffer
Integer divide number by 10
If negative flag is set
Write '-' into next position in temp buffer
Write characters in temp buffer into output string in reverse order

И реализация на C#:

    1 /// <summary>
    2 /// Converts integer value to int string representation.
    3 /// </summary>
    4 /// <param name="value">Target integer value.</param>
    5 /// <returns>String representation of specified value.</returns>
    6 public static String Int32ToString(Int32 value)
    7 {
    8     char[] output = new char[10];
    9     bool isNegative = false;
   10     int i = 0;
   11 
   12     // First of all, check whether value is negative.
   13     if (value < 0)
   14     {
   15         isNegative = true;
   16         value *= -1;
   17     }
   18 
   19     do
   20     {
   21         // Find current number and shift to the corresponding char.
   22         output[i++] = (char)((value % 10) + '0');
   23 
   24         // Divide by 10, so on the next iteration we still 
   25         // can obtain valid last number.
   26         value /= 10;
   27     }
   28     while (value > 0);
   29 
   30     // Add a minus sign "-" if isNegative flag is set.
   31     if (isNegative)
   32     {
   33         output[i] = '-';
   34     }
   35 
   36     // Construct the output string.
   37     string result = string.Empty;
   38     int position = output.Length - 1;
   39     while (position >= 0)
   40     {
   41         if (output[position] != '\0')
   42         {
   43             result += output[position];
   44         }
   45         position--;
   46     }
   47 
   48     return result;
   49 }

В следующий раз я раскажу как сделать обратное - из строки число.

Happy coding...

Algorithms: Distinct an array

2009-03-21T06:40:00.000-07:00

Внимание
Код приведенный в этой заметке написан на C#.

Задача: дан отсортированный массив целых чисел. Необходимо удалить в массиве все повторения и получить массив, в котором сначала идут неповторяющиеся числа, а остальные элементы массива должны быть заполнены нулями.

Рассмотрим простой пример. Возмем массив в котором есть 2 повторяющихся числа: {1, 2, 3, 3, 4, 5, 5, 5, 6}. В данном массиве числа 3 и 5 повторяются несколько раз. В результате необходимо вернуть массив: {1, 2, 3, 4, 5, 6, 0, 0, 0}.

Приведу возможное решение задачи (коментарии по коду):

    1 /// <summary>
    2 /// Task: distinct an array.
    3 /// Requirements: array of integers, sorted in ascending order. 
    4 /// Use the same array object and return its distinct value. 
    5 /// Distinct values should come first, and the remaining 
    6 /// elements must be filled with zeros.
    7 /// For instance: 
    8 /// {1, 2, 2, 3, 4, 4, 5 } => {1, 2, 3, 4, 5, 0, 0}.
    9 /// 
   10 /// Complexity: O(n).
   11 /// </summary>
   12 /// <param name="input">Target array.</param>
   13 /// <returns>Distinct array.</returns>
   14 public static int[] DistinctArray(int[] input)
   15 {
   16     // First of all, we need to check the input array.
   17     if (input == null || input.Length == 0)
   18     {
   19         throw new ArgumentNullException("input");
   20     }
   21 
   22     int position = 0;
   23     for (int index = 1; index < input.Length; index++)
   24     {
   25         if (input[index] != input[position])
   26         {
   27             input[++position] = input[index];
   28         }
   29     }
   30 
   31     for (int index = position + 1; index < input.Length; index++)
   32     {
   33         input[index] = 0;
   34     }
   35 
   36     return input;
   37 }

Такое решение имеет сложность O(n).

И в заключение - пример использования:

    1 int[] inputArray = { 1, 2, 3, 3, 4, 5, 5, 5, 6 };
    2 inputArray.PrintArray();
    3 var outputArray = ArrayUtilities.DistinctArray(inputArray);
    4 outputArray.PrintArray();

Запускаем, и....

PS:

наверное у кого-то может возникнуть вопрос: "как так получилось - inputArray.PrintArray()?" - так вот это всего лишь вспомогательный extension-метод. Приведу его кот потому что он может нам (мне и тебе ув. %username%) еще пригодится.

    1 /// <summary>
    2 /// Prints an array.
    3 /// </summary>
    4 /// <typeparam name="T">Array type.</typeparam>
    5 /// <param name="input">Input array instance.</param>
    6 public static void PrintArray<T>(this T[] input)
    7 {
    8     if (input == null)
    9     {
   10         Console.WriteLine("Input array is null.");
   11         return;
   12     }
   13 
   14     Console.Write(typeof(T).Name + "[" + input.Length + "] = {");
   15     for (var index = 0; index < input.Length; index++)
   16     {
   17         Console.Write(input[index]);
   18         if (index < input.Length - 1)
   19         {
   20             Console.Write(", ");
   21         }
   22     }
   23     Console.WriteLine("}");
   24 }

В следующий раз я раскажу как перевести число в строку :) (без использования int.ToString()).

Happy coding...