CodeChef JULY long and cookoff problems

My performance was bad in July. Could solve 2 problems in the long contest:CSUB, RETPO and 2 in the Cookoff: RRCOPY, RRSUM.

Got stuck with FROGV in the long contest and FRNDS in the Cookoff. Need to do better.

Read Anudeep's blog to get more inspiration: 
http://blog.anudeep2011.com/ioi-and-acm-learning-community/
http://blog.anudeep2011.com/when-2-guys-talk-its-not-always-about-girlssports/

Neat introduction to Combinatorial games

I was looking to solve Hackerrank w7 challenges and one problem was about the game of Nim. After that, I started to look up good introductions to Nim. I found this one interesting: comb.pdf

I found it very useful to understand the game.

This one talks about Backward induction, P-positions and N-positions. Just what is required.