Now, Accuracy comes with solving problems! Please read the contribution guidline!

So, here presented before you a repository housing the largest collection of problems (and their solutions, of course). Make this the one and only repository where people can turn to when they want to practice problem solving and if somebody is stuck in some programming problem in some coding contest. But, I don't encourage you to look at the solution right away. First understand the problem, do some brainstorming and if you still can't solve, go for the solution!