I am new to programming.
I really don’t understand how the points are awarded in the questions which have points(eg NOPC9 string encryption),my execution time was 0.00 sec yet I was awarded 0.5 points. What does the chef look for while awarding the point,in the code?
PS: I searched for it in the site but couldn’t find it.
@coda : The points are not awarded on the basis of execution time / memory consumed . For every challenge problem there is a different marking scheme which is mentioned with the problem statement . You score is the ratio of your score with the score of best submitted solution till that time . The score is dynamic , so if someone submits a solution with a score better than the current best , then the new person gets score of 1.0 and everyone else’s ratio if recalculated .
I was not able to find the NOPC9 string encryption problem , please tell the exact problem code .
the NOPC9 problem is in the peer section, but points are rewarded as it was in the challenge one. probably a simple little mistake. nothing to really worry about, considering the fact that you have clearly explained to @coda the way points are rewarded for this kind of problems. 
It seems to me that there is partial score used (I didn’t know it is possible here).
So there are 8 files and your program returns correct result just for 4 of them.
Problem is f.e. with that input:
abc
your code returns
a1b1thax a lot guys