I am new to CP and I have seen comments from many experienced programmers about how they couldn't figure out the problem but got it accepted using randomization. Any information / link to blogs / tutorials about this technique would be helpful to me.

I am really having difficulty in understanding some pattern searching algorithms like Z function, KMP , Robinson karp algorithm can you please suggest some good tutorials or videos for the same. I have tried to watch some videos on youtube but was unable to understand from them. Also use of Z function came in one recent contest on codeforces so I am eager to learn it as a part of up solving for that contest.

What to learn from a problem which you were not able to solve in a contest and the solution consists mostly of adhoc/non-trivial observations.