codingfreak

12.02.2013

Displaying MATH formulas in blogger

Introducing math formulas in blogger was a daunting task in olden days. Now using Mathjax we can include them without any issue. Let us see steps to add support for Mathjax to blogger template.

1. In your blog default home page under "template" section select "Edit HTML" option. Add following line after <head> tag

<script type="text/javascript"
   src="http://cdn.mathjax.org/mathjax/latest/MathJax.js?config=TeX-AMS-MML_HTMLorMML">
</script>

2. Now we can include math formulas as simple ASCII Math notation.

NOTE: We should use ∖( ...∖) for inline math and ∖[ ... ∖] for displayed math.

For inline math

To display \(\left(x-1\right)\left(x+3\right) \sqrt{a^2+b^2}\) as inline formula

Similarly for displayed math

\[\sqrt{a^2+b^2}x = a_0 + \frac{1}x = a_0 + \frac{1}{\displaystyle a_1 + \frac{1}{\displaystyle a_2 + \frac{1}{\displaystyle a_3 + a_4}}}{a_1 + \frac{1}{a_2 + \frac{1}{a_3 + a_4}}}\]
References:

1. Mathjax
2. Online Latex Editor

11.04.2013

Bubble Sorting

Bubble sort is one of the simple sorting algorithms and also popularly known as a Brute Force Approach. The logic of the algorithm is very simple as it works by repeatedly iterating through a list of elements, comparing two elements at a time and swapping them if necessary until all the elements are swapped to an order.

For e.g. if we have a list of 10 elements, bubble sort starts by comparing the first two elements in the list. If the second element is smaller than the first element then it exchanges them. Then it compares the current second element with the third element in the list. This continues until the second last and the last element is compared which completes one iteration through the list. By the time it completes the first iteration the largest element in the list comes to the rightmost position.

Image courtesy from Annieink.com

The algorithm gets its name as we start from lowest point and “bubble up” the higher elements to the highest point in the list. We can also follow other approach where we start from highest point and “bubble down” lowest elements in the list. Since it only uses comparisons to operate on elements, it is a comparison sort.

Reality of a Software Project

That's the reality I faced in real world crappy planning of Software Project. As a Developer we never have "FREE TIME" ..

Reality of a Software Project

6.10.2013

How to narrate a story to computer scientist

If it brings back old memories or a smile then I hope you understood the characters in STORY.

3.15.2013

Death of Google Reader - Journey towards alternatives

Flashback

Long Long ago when INTERNET is booming up with so many websites its really hard to follow the interesting one. Its quite clumsy to go around miliions of sites to check for new posts.

Am I Doomed ?

No, you are not. RSS feed mechanism is the answer.

Just follow the RSS feed of your favourite site and the RSS reader will maintain the unread articles, favourite articles and so on. Voilla simple and effective solution to follow various sites.

Divide a number by 3 without using any arithmetic operators

How to divide a number by 3 without using operators + - / * %

NOTE: I am just trying to collect various answers down in this post available across multiple sites in internet as mentioned in references.

Solution 01:

#include <stdio.h>
#include <stdlib.h>

int main()
{
    FILE *fp=fopen("temp.dat","w+b");
    int number=12346;
    int divisor=3;
    char *buf = calloc(number,1);
    fwrite(buf,number,1,fp);
    rewind(fp);
    int result=fread(buf,divisor,number,fp);
    printf("%d / %d = %d", number, divisor, result);
    free(buf);
    fclose(fp);
    return 0;
}

Checking Balance of Symbols in a expression

This article is part of article series - "Datastructures"

A balanced expression contains right number of closing and open braces.

For example:

[[ - unbalanced expression
[]{}() - balanced expression
[(*)] - balanced expression

Let us see how to find if an expression is balanced or not by checking for following operators [ ] { } and ( ) in the given expression.

Using Stacks

Conversion from Infix to Postfix

This article is part of article series - "Datastructures"

Converting a Fully Parenthesized Infix expression into Postfix expression

Analysis:

Five types of input characters

Opening parentheses
Operands
Operators
Closing parentheses
New line character (\n)

Pseudocode:

********************************************************  
 Function  : main  
  
 Calls     : createStack  
             freeStack                
             pushIntoStack   
             popFromStack   
  
 Called by : NONE   
  
 Input   
 Parameters: Accepts input expression for processing  
    
 Returns   : Converts Fully paranthesized INFIX 
             expression into POSTFIX expression
******************************************************** 

SET i to 0
GET infix expression from user into input_array
SET var with input_array[i]

CALL createStack

WHILE var != end of string

  IF var equals to '(' THEN
  
    CALL pushIntoStack (stack, var)  

  ELSE IF var is a number THEN        
  
    PRINT var  

  ELSE IF var is an arithmetic operator THEN
  
    CALL pushIntoStack (stack, var) 
    
  ELSE IF var equals to ')' THEN

    WHILE stackTop != '('

      IF stackTop is an arithmetic operator THEN

        PRINT stackTop
        popFromStack (stack)

      ENDIF
    
    ENDWHILE

    popFromStack (stack)

  ENDIF

  SET var with input_expression[INCREMENT i]

ENDWHILE

CALL freeStack (stack)

Deleting a Node from a Singly Linked List

This article is part of article series - "Datastructures"

Previous Article: Implementation of Singly Linked List.
Next Article: Reversing a Singly Linked List

Deletion of a Node from a Singly Linked List
Similar to insertion we have three cases for deleting a Node from a Singly Linked List.

Deleting First Node in Singly Linked List

To complete deletion of firstNode in the list we have to change Head pointing to Next of firstNode.

Pseudocode:
```
firstNode = Head

Head = firstNode->Next

free firstNode
```
Complexity:
Time Complexity: O(1)
Space Complexity: O(1)

Detecting First Node in a Loop in the List

This article is part of article series - "Datastructures"

Previous Article: Detecting a Loop in Singly Linked List - Tortoise and Hare.
Next Article: Finding Nth node from end of a Singly Linked List.

Once we confirm that there is a Loop in a Singly Linked List we will see how to determine first node of the loop.

Finding Nth node from end of a Singly Linked List

This article is part of article series - "Datastructures"

Previous Article: Finding first node in a Loop in Singly Linked List.

Figure 1: Singly Linked List

Solution 01 - Brute Force Approach:

Start at First Node of the List (call it curNodePtr).
Assign curNodePtr to tmpPtr and count number of nodes after the curNodePtr.
If number of nodes after curNodePtr are equal to N nodes or tmpPtr reaches END then break. If tmPtr reaches END but count not equal to N then return since we can't find the Nth node from the end of the Singly Linked List.
Move the curNodePtr one step forward in the Linked List i.e curNodePtr now points to its next node in the list and start again from STEP-2.

Reversing a Singly Linked List

This article is part of article series - "Datastructures"

Previous Article: Deleting a Node from a Singly Linked List.
Next Article: Detecting a Loop in Singly Linked List - Tortoise and Hare.

Let us see how to reverse a Singly Linked List.

Figure-1: Singly Linked List

Pseudocode:

cur_ptr = HEAD->NEXT
prev_ptr = NULL

forever:

   if cur_ptr == NULL
   break

   tmp_ptr  = prev_ptr
   prev_ptr = cur_ptr
   cur_ptr  = cur_ptr->NEXT
   
   prev_ptr->NEXT = tmp_ptr

HEAD->NEXT = prev_ptr

Complexity:
Time Complexity: O(n)
Space Complexity: O(3)

If we try on the example in Figure-1 we get the output as shown below

Figure-2: After reversing the Singly Linked List

Previous Article: Deleting a Node from a Singly Linked List.
Next Article: Detecting a Loop in Singly Linked List - Tortoise and Hare.

9.21.2012

Detecting a Loop in Singly Linked List - Tortoise & Hare

This article is part of article series - "Datastructures"

Previous Article: Reversing a Singly Linked List.
Next Article: Finding first node in a Loop in Singly Linked List.

Eventhough there are multiple algorithms available we start with

Floyd's Cycle-Finding Algorithm
In simple terms it is also known as "Tortoise and Hare Algorithm" or "Floyd's Cycle Detection Algorithm" named after its inventor Robert Floyd. It is one of the simple cycle detection algorithm. It's a simple pointers based approach.

Robert Floyd

Write a C Program without main function

In a C program main function is the entry point so it is mandatory to have a main function.

But let us see how can we write a program without main (Kind of hiding main in some obfuscated code). This post is purely out of interest to know that we can do something weird like this, just for learning.

Implementing ls command in C

We know that ls command in unix displays the list of files in a directory. It has various options to display the data in various styles and formats.

By default its implementation is part of Coreutils package, which is default package in all Linux flavours.

I want to see how we can implement its basic functionality with a simple C program.

GIT - Adding diffmerge as visual merge in git

GIT is one of the popular distributed code repositories in opensource community, especially with developers working on opensource projects like linux kernel and others.

Operations like Merge and Diff are the most irritating & tricky tasks via command line when working on large code changes. So let us see how can we add some graphical stuff for these operations when using on GIT so that we can do merging and other options very easily.

TCPDUMP cheat sheet

Decoding hardware information of a PC

Checking out machine hardware information is no more a geeky thing of olden days where you need to go through the hardware specification documents or to open up a physical machine to find out the hardware details if the specification documents are missing. Now we have some really cool handy software tools to help us out.

I thought to make a page with some important tools which help us in decoding the hardware related information on a Linux Box. Feel free to drop a comment with the tool names I missed out in this post.

NOTE: All of them are ordered in alphabetical order and I am trying these tools on a Ubuntu machine running in virtual box. So some of the tool outputs might be displaying names likes VirtualBox and Oracle Corporation.

Uli Drepper - Basics you should know about buffer overflow

Part 1: Buffer Overflows

Connecting via SSH without password prompt

SSH is the common way to connect remote machines these days. Almost all kinds of applications use SSH in background for communicating with end machines.

But sometimes typing password repeatedly for establishing a SSH connection with the trusted end machine is quite daunting task.

Let us see how to automate the things in 3 simple steps where we can ssh to "user@host" without asking a password every time. Replace user with the username and host with the remote machine ip-address or hostname. For E.g. john@192.168.245.129

NOTE: Only do this with trusted machines.

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Pages

12.02.2013

11.04.2013

8.13.2013

6.10.2013

3.15.2013

3.13.2013

Using Stacks

2.05.2013

Converting a Fully Parenthesized Infix expression into Postfix expression

Analysis:

Pseudocode:

12.25.2012

11.13.2012

11.06.2012

9.21.2012

8.23.2012

8.09.2012

7.11.2012

6.14.2012

5.02.2012

4.19.2012

4.05.2012