codility, and the like websites?
These websites present problems in computer science. I always find it difficult to solve, however you see other guys solve these problems very fast. 

What kind of knowledge that is required to be proficient to solve those kinds of problems ?

An algorithms book like CLR doesn't even help...  
codility, and the like websites?
===

These websites present problems in computer science. I always find it difficult to solve, however you see other guys solve these problems very fast. 

What kind of knowledge that is required to be proficient to solve those kinds of problems ?

An algorithms book like CLR doesn't even help...  