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The above link has a lot of tutorials to master yourself in Algorithmic C/C++ Programming . The tutorials are very well explained with lots of examples and practise problems . Its a very good way to learn algorithms .

The tutorials are written by World’s Best Programmers accross the Globe , so you can expect great clarity and efficiency. I assure you that it will be a very enjoyable experience !

Learning the Standard Template Library (STL) :

Today no programming contest uses the Borland’s C/C++ Compiler. Every popular contests require the programmers to code in accordance to GCC/ G++ Compiler ( GNU C Compiler ). It has a lot of improvements and new datastructures , and thus makes programming a very comfortable and pleasurable experience. So , learning the STL is almost a must in today’s scenario.

The best place to Learn STL : http://www.topcoder.com/tc?module=Static&d1=tutorials&d2=standardTemplateLibrary

An awesome Problem Arcive :  http://www.topcoder.com/tc?module=ProblemArchive

For beginners : http://www.topcoder.com/tc?module=ProblemArchive&sr=&er=&sc=&sd=&class=&cat=&div1l=&div2l=1&mind1s=&mind2s=&maxd1s=&maxd2s=&wr=

The above link gives you a lot of very easy problems and helps you a lot to improve your programming skill and to develop a sequential logicalcal flow to solve problems .

Once you are comfortable solving the Division 2 Level 1 Problems , you can proceed to Division 2 , Level 2 Problems .

Some world-class Problems : http://www.spoj.pl/problems/classical/

I would suggest one not to try the above link before gaining a good grip in Algorithm Programming from TopCoder . Trust me , it could be very de-motivating to be unable to solve even a single problem .

Programming Contest Calender : http://www.algorithmist.com/index.php/Programming_Contest_Calendar .

Hey visitor, pass the word about this blog if you find it useful.

Feel Free to Leave Your Comments .

Also check out my other article about participating in Algorithm Competitions.

1. Dont use:
for(int i=0;i<strlen(str);i++)
{ … }

Instead use
int l=strlen(str);
for(int i=0;i<l;i++)
{ … }

Each time you call strlen() , it manually goes through the array counting each character. Suppose the string length is 1000. The first loop will take 1000*1000 operations as strlen is called for every iteration. The second loop takes only 1000 operations ( excluding what goes on inside the loop of course )

2. Size() returns unsigned int :
And if you use something like
for(int i=0;i<A.size() – 2 ;i++)
{ … }
Where A is a vector, when the size of the vector is less than 2 , the loop still executes abs( A.size() – 2 ) times since size() returns an unsigned int and when we subtract a number from an unsigned int we get an unsigned int

3. Don’t use long long everywhere in your program. Its very slow compared to int.

4. scanf() is faster then cin .

5. Arrays are faster than vectors.

Some usual errors from the online judge :

• Time Limit Exceeded – A very familiar judge result on Spoj. It means your program took too long to execute. Try optimizing your program and check for accidental infinite loops.

• Wrong Answer – Your program ran on time, but it did not produce the required output.

• Compile Error -Your program had some syntax error. For these errors, click on the text “Compile Error” in the judge result. It`ll take you a page which will list the compile errors and their line numbers in your program.

• Runtime Error – This is usually accompanied by a code like SIGSEV. It can happen due to a lot of reasons, but the two most common are using too much memory ( you can use around 6000*6000*4 bytes of memory ). Other reasons can be there like Divide by Zero.

Conclusion :
“Practice makes a man perfect”
Practice, practice and more practice is all that it takes to reach the top.

Hey visitor, pass the word about this blog if you find it useful.

Feel Free to Leave Your Comments .

- Vidya Sagar , I year , CSE , SASTRA University , India
TopCoder handle : s4sagar
TopCoder profile: http://www.topcoder.com/tc?module=MemberProfile&cr=22652618