Download it here : Social Connect Buttons [psd]

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How can I dynamically hide any element using Javascript ?

The obvious solutions to this is to set "display" style to "none". Something like this:

document.getElementById('element').style.display = 'none';

This will surely work, but is it the correct way to do so? May be not, as you would face problems in showing that element again. The problem in showing that element is that you don't know the original display property of that element. Whether it was a "Block" level element or an "inline" element. So, basically you'll have to do something like this, depending upon type of element:

document.getElementById('element').style.display = 'block';
document.getElementById('element').style.display = 'inline';

Can we do it in some better way?

Now do it proper way

An improved way to achieve similar thing is to create a css class like this:

.hide{display:none !important;}

And now just add or remove this class to hide and show elements.

document.getElementById('element').className = 'hide';

or write $("element").addClass('hide'); if you are using mootools.

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2. Show IMDB Ratings on Torrentz.com using GreaseMonkey Script
3. Vertical-Align : Middle Using Javascript : JQuery & Mootools

How to Install Git on Webfaction

1. Log into your Webfaction Control Panel
2. Navigate to Domains/Websites » Applications
3. Click Add New
4. Enter git as the application name in the Name field
5. Select git from the App category menu
6. Enter a password for the default user in the Extra Info field
7. Click the Create button

The Git application provides a subdirectory, bin, which contains the Git executables. It also provides a subdirectory, repos, to store your Git repositories. repos/proj.git has been created automatically as an example.

Later you'll have to create a Website (Domain/Website -> Website, in Control Panel), which maps this newly created Git application to some subdomain. For further explanation i'll assume this domain to be "git.domain.com"

If you want you can delete existing proj.git by simply deleting this directory.
rm -r ~/webapps/git/repos/proj.git

Create a new Git Repository

1. Open an SSH session to your webfaction account: ssh username@username.webfactional.com
2. cd ~/webapps/git/
3. ./bin/git init --bare ./repos/reponame.git
   This will create a new repository, where reponameis the name of your repository
4. cd repos/repo.git
5. ../../bin/git config http.receivepack true
   This will enable HTTP push to repository

Pushing local code to this repository

1. cd /path/to/your/local/repository/
2. git init If it’s not already under version control
3. git add .
4. git commit -a -m 'Initial commit.'
5. If you want to use SSH mode then
   git remote add origin ssh://username@git.domain.com/~/webapps/git/repos/reponame.git
   For HTTP Mode
   git remote add origin http://username@git.domain.com/reponame.git
6. git push origin master
7. git push

Final Command should give you Everything up-to-date message.

Introduce Yourself to Git Server

It is a good idea to introduce yourself to git with your name and public email address before doing any operation. The easiest way to do so is:
git config --global user.name "Nitin Hayaran"
git config --global user.email you@yourdomain.example.com

Troubleshooting

On giving git push origin master command git may throw error error: RPC failed; result=22, HTTP code = 411. It will show you message like this:

Compressing objects: 100% (792/792), done.
error: RPC failed; result=22, HTTP code = 411
Writing objects: 100% (1148/1148), 18.79 MiB | 13.81 MiB/s, done.
Total 1148 (delta 356), reused 944 (delta 214)

This error comes when either your code size is big, or there is any file with big size. To solve this problem you need to increase buffer size in Git configuration.
git config http.postBuffer 524288000

Clone Your Repository Somewhere New

With SSH Mode Setup
git clone username@git.domain.com:webapps/git/repos/reponame.git
For HTTP Push Mode
git clone http://username@git.domain.com/reponame.git

Further Information

• Webfaction’s Git Documentation

The Third and final problem of the Facebook Qualification 2011 Round was Studious Student. The problem goes like this:

Studious Student

You've been given a list of words to study and memorize. Being a diligent student of language and the arts, you've decided to not study them at all and instead make up pointless games based on them. One game you've come up with is to see how you can concatenate the words to generate the lexicographically lowest possible string.

Input

As input for playing this game you will receive a text file containing an integer N, the number of word sets you need to play your game against. This will be followed by N word sets, each starting with an integer M, the number of words in the set, followed by M words. All tokens in the input will be separated by some whitespace and, aside from N and M, will consist entirely of lowercase letters.

Output

Your submission should contain the lexicographically shortest strings for each corresponding word set, one per line and in order.

Constraints

1 <= N <= 100
1 <= M <= 9
1 <= all word lengths <= 10

Example input

5
6 facebook hacker cup for studious students
5 k duz q rc lvraw
5 mybea zdr yubx xe dyroiy
5 jibw ji jp bw jibw
5 uiuy hopji li j dcyi

Example output

cupfacebookforhackerstudentsstudious
duzklvrawqrc
dyroiymybeaxeyubxzdr
bwjibwjibwjijp
dcyihopjijliuiuy

Analysis and Solution

This problem is a most confusing out of the lot. Me myself made a silly mistake while solving this problem. On first look it looks like the problem should get solved by sorting and joining the strings, but its not like that.

Consider this following input:

jibw ji jp bw jibw

By sorting and concatenate, the answer should be is:

bwjijibwjibwjp

However, lexicographically lowest possible string will be:

bwjibwjibwjijp

Notice in the above words, "ji" is the prefix of "jibw". The "sort and concatenate" method definitely does not work when there is a case where a word is a prefix of one or more other words.

Some of the contestants solved this problem with brute force, as input range was not that big. With M<=9 one could have only 9!= 362880 possible permutations. And answer can be obtained by sorting these permutations.

However, I didn’t went this approach. I used python internal Sort function with custom compare. Here is my code

Related posts:

1. Facebook Hacker Cup : Peg Game Problem Solution
2. Facebook Hacker Cup : Double Squares Problem Solution

Continuing with my earlier solution of the First Problem “Double Square”, here is solution and analysis for Second Problem “Peg Game”

Peg Game

At the arcade, you can play a simple game where a ball is dropped into the top of the game, from a position of your choosing. There are a number of pegs that the ball will bounce off of as it drops through the game. Whenever the ball hits a peg, it will bounce to the left with probability 0.5 and to the right with probability 0.5. The one exception to this is when it hits a peg on the far left or right side, in which case it always bounces towards the middle.
When the game was first made, the pegs where arranged in a regular grid. However, it's an old game, and now some of the pegs are missing. Your goal in the game is to get the ball to fall out of the bottom of the game in a specific location. Your task is, given the arrangement of the game, to determine the optimal place to drop the ball, such that the probability of getting it to this specific location is maximized.

The image below shows an example of a game with five rows of five columns. Notice that the top row has five pegs, the next row has four pegs, the next five, and so on. With five columns, there are four choices to drop the ball into (indexed from 0). Note that in this example, there are three pegs missing. The top row is row 0, and the leftmost peg is column 0, so the coordinates of the missing pegs are (1,1), (2,1) and (3,2). In this example, the best place to drop the ball is on the far left, in column 0, which gives a 50% chance that it will end in the goal.

x.x.x.x.x
 x...x.x
x...x.x.x
 x.x...x
x.x.x.x.x
 G  

'x' indicates a peg, '.' indicates empty space.

Input

You should first read an integer N, the number of test cases. Each of the next N lines will then contain a single test case. Each test case will start with integers R and C, the number of rows and columns (R will be odd). Next, an integer K will specify the target column. Finally, an integer M will be followed by M pairs of integer r_i and c_i, giving the locations of the missing pegs.

Constraints

• 1 ≤ N ≤ 100
• 3 ≤ R,C ≤ 100
• The top and bottom rows will not have any missing pegs.
• Other parameters will all be valid, given R and C

Output

For each test case, you should output an integer, the location to drop the ball into, followed by the probability that the ball will end in columns K, formatted with exactly six digits after the decimal point (round the last digit, don't truncate).

Notes

The input will be designed such that minor rounding errors will not impact the output (i.e. there will be no ties or near — up to 1E-9 — ties, and the direction of rounding for the output will not be impacted by small errors).

Example input

4
5 4 0 1 2 2
3 3 1 2 1 1 1 0
3 4 0 2 1 0 1 1
3 4 0 1 1 1

Example Output

0 0.375000
1 1.000000
0 1.000000
0 0.500000

Analysis and Solution

This is the hardest problem of the lot, and I also spent hours to understand the problem statement. If you are also among those who haven’t got this problem then, I would recommend you to read its explanation here.

Once I understood problem statement, next hurdle was to have map this in programming paradigm. I went with a double size two-dimension array [row*2, col*2], to hold complete Input. Basically it was holding both Pegs, and Pits(blank space from where ball can pass).

For solving the problem I approached it from bottom, assuming that to get ball at X and probability 1. Then we move to above row and back calculate possible probabilities for every pit.

The code to solve this problem is:

Related posts:

1. Facebook Hacker Cup : Studious Student Problem Solution
2. Facebook Hacker Cup : Double Squares Problem Solution

A lot of people have participated and qualified in Qualification Round of Facebook Hacker Cup. Luckily I am also qualified for First Round. Facebook Hacker Cup Qualification Round consisted 3 problems. All of these problems were programmatically easy but tricky. Lots of people made very simple mistakes while solving these problem(including me).

First Problem of the round was:

Double Squares

A double-square number is an integer X which can be expressed as the sum of two perfect squares. For example, 10 is a double-square because 10 = 3²+ 1². Your task in this problem is, given X, determine the number of ways in which it can be written as the sum of two squares. For example, 10 can only be written as 3² + 1² (we don't count 1² + 3² as being different). On the other hand, 25 can be written as 5² + 0² or as 4² + 3².

Input

You should first read an integer N, the number of test cases. The next N lines will contain N values of X.

Constraints

0 ≤ X ≤ 2147483647
1 ≤ N ≤ 100

Output

For each value of X, you should output the number of ways to write X as the sum of two squares.

Example input

5
10
25
3
0
1

Example output

1
2
0
1
1

Analysis and Solution

This problem was by far the easiest of the lot. But as Facebook title for the problem said “Too hard for brute force, switching to dp”, this problem was almost impossible to be solved with Brute Force.

The strategy I used was quite simple. If we consider M is the given number, and we want to find out x, y such that:

M = x^2 + y^2

So basically we’ll loop from 0 to sqrt(M) and will find out D such that:

D = M – i*i

and if D is square root is an integer then, this number is a double square.

The python code of this problem is:

Related posts:

1. Facebook Hacker Cup : Studious Student Problem Solution
2. Facebook Hacker Cup : Peg Game Problem Solution

So here is the python function to do that:

def title(value):
    """Converts a string into titlecase."""
    t = re.sub("([a-z])'([A-Z])", lambda m: m.group(0).lower(), value.title())
    return re.sub("\d([A-Z])", lambda m: m.group(0).lower(), t)

Happy Coding

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I don’t know when this picture was taken, or is it actually of India or not, but condition of Indian Railways is not a lot different from this. The trains are always crowded, and it is difficult to get reservation in train. Every train traveler might faced the problem of non-availability of tickets in Indian Railways. Anyways, here I am not going to discuss the condition of Indian Railways.

In this post I want to Introduce one of the web-service which I built for my use, and I think it would be useful for you as well.

The name of the website is PNRCheck.com. The website will help you to keep track of your waiting list / RAC tickets. The process is very simple:

1. You need to login to the website.
2. Submit your 10 digit PNR Number for tracking, and relax.
3. We’ll send you an SMS and E-mail as and when the ticket gets confirmed. Even if the ticket doesn’t gets confirmed we’ll send you the final status of ticket(on chart preparation).

By using this service you won’t have to go and check for ticket confirmation again and again, and I think this will definitely save some of your time.

How does it work

Its plain and simple, the service keeps checking for any update of your ticket from indianrail.gov.in. And whenever it sees that your ticket is confirmed, it shoots you an email and SMS about latest status of the ticket.

As this service is dependent on availability from IndianRail.gov.in, there might be some instances where, you are not able to see updated status, or the website is not allowing you  to submit new tickets. In such instances I’d request you to kindly wait for some time and try again later, otherwise you can also try checking your ticket status from indianrail.gov.in.

Why PNRCheck.com?

The only reason, for creating pnrcheck.com is that, such a service is very much required. This service must be provided by Indian Railways in first place. They take decent amount of service charges from us, and can’t simply send us update about our ticket.

Lets start using this service may be Indian Railways will get some lessons from this and may be later they start sending us these updates. So I’d request you to please tell your friends about this website, so that more and more people can use this service.

PNRCheck.com Beta

The website is presently is in beta, so there might be some glitches here and there. I’d request you to kindly post your comments, feedback, errors through feedback button on left side of your screen.

Let me here thoughts about this service through comments.

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This javascript turns the webpage black if there is no user activity on the page for some time. As the page predominantly turn black the script in-effect saves energy.

Image displayed is primarily a function of the user's color settings and desktop graphics, as well as the color and size of open application windows; a given monitor requires more power to display a white (or light) screen than a black (or dark) screen.

Roberson et al, 2002.

Just have a look at the Demo to see how it looks:

Energy Saving Javascript Demo

How to Use

Using this script is damn simple just place following script tag anywhere in the page. It would be good if you place this script just before </body>

<script src="http://apps.nitinh.com/energy.js?time=100&amp;credit=0" type="text/javascript"></script>

Configuration

There are two configurable parameters:

• time : This is the amount of idle time before which the screen turn black. The time is in number of seconds and its value should be greater than 10.
• credit : This is boolean field to show / hide credits in Black Screen. Values could be 1 or 0

Hope this script saves some of the valuable world energy.

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WordPress is an excellent blogging engine. It is easy to setup and even easier to use. It has got a huge collection of themes and plugins. Because of all these things WordPress has got so widespread use.

WordPress has the concept of categories to segregate posts in different types.  When number of posts in some category becomes really huge, its good to make a separate website for this particular category.

I faced similar problem for one of my website and I decided to migrate all of my posts in “XYZ” category to a different domain. But, unfortunately WordPress Admin Dashboard doesn’t provide any direct method to export all posts in a particular category.

So, to perform such migration we’ll have to go through several steps. For better understanding we can basically divide this full migration in two steps:

1. Export Posts / Comments based on its category
2. Redirect posts of this category

Export Posts based on its category

WordPress admin panel is very rich, and it does provide direct method to export posts, pages, comments, custom fields, categories, and tags. But you can only export it based on its author, there isn’t any way based on category. So, basically what I did was :

1. Create a new user “AUTHOR_1”
2. Change author of all the posts in category “CATEGORY_XYZ” to “AUTHOR_1”
3. Export posts of “AUTHOR_1”

Step 1 and 3 are quite obvious and straight, the only challenge is with Step 2. The best way I felt was to dig into the WordPress database and change author on table level itself.

Database Manipulation

WordPress stores all posts in a table called “wp_xxxxxx_posts”. This table consists a column named “post_author”. So basically we’ll have to change this column for our posts. To do this just run following queries on your wordpress database.

NOTE : Before running any query on database level, I’ll recommend you to take backup of the datebase.

Get TERM_ID

SELECT  `term_id` ,  `name` ,  `slug`
FROM  `wp_h8kac5_terms`
WHERE  `name` LIKE  'CATEGORY_XYZ'

Here you'll have to note the "term_id" In following query put term_id taken form above query.

Get TERM_TAXONOMY_ID

SELECT  `term_taxonomy_id` ,  `term_id` ,  `taxonomy` ,  `count`
FROM  `wp_h8kac5_term_taxonomy`
WHERE  `term_id` = %term_id%
AND taxonomy =  'category'

Here you have to note "term_taxonomy_id". Secondly you can see a column "count", this count should be equal to the posts returned in :

http://www.example.com/wp-admin/edit.php?category_name=CATEGORY_XYZ

Update AUTHOR_ID in Posts Table

This is the final sql query to update author. Before this you need to find the user_id of the user we just created. This can be found in table "wp_h8kac5_users".

UPDATE wp_h8kac5_posts
SET post_author = %USER_ID%
WHERE id IN (
SELECT object_id FROM `wp_h8kac5_term_relationships` WHERE `term_taxonomy_id` = %TERM_TAXONOMY_ID% )

You need to replace %TERM_TAXONOMY_ID% from the "term_taxonomy_id" returned from the previous query.

Export Posts

Hurry !! half the battle is won. We have changed author of all the desired posts. Now we just have to log on to admin panel and export the posts of this author. This can be done from:

http://www.example.com/wp-admin/export.php

Imports Posts on New Domain

Now log on to the admin dashboard of new domain and import these posts from:

http://www.example.com/wp-admin/import.php

At at this point we have done with export part of this migration process. Now the only thing left is to redirect these posts. For redirection we’ll use .htaccess rules.

Redirect posts of the category

On my website I have following permalink format :

/%year%/%monthnum%/%category%/%postname%/

So, basically “Category” is the 3rd parameter in my URL Scheme. You need to keep similar URL Scheme on your new website. According to this URL pattern we have to write a rule in .htaccess file.

# BEGIN Redirection

RewriteEngine On
RewriteCond %{REQUEST_URI} ^(/\d{4}/\d{2}/)([^/]+)(/.*)$
RewriteCond %2 ^CATEGORY_XYZ$
RewriteRule ^(.*)$ http://www.new-domain.com/$1 [redirect=permanent,last]

# END Redirection

Just put above code in starting of .htaccess, and you are all done.

You can test our implementation by visiting any post of “CATEGORY_XYZ”, it should be redirected to your new domain.

Feel free to shoot any queries through comments.