Level: Expert

Link: https://www.hackerrank.com/challenges/string-similarity

Algorithm: Z-Algorithm
Efficiency: O(N)
Python Link:
http://codereview.stackexchange.com/questions/53852/z-algorithm-for-pattern-matching-in-strings
Level: Easy

Link: https://www.hackerrank.com/challenges/anagram
Level: Easy

Link: https://www.hackerrank.com/challenges/game-of-thrones
Level: Moderate

Link: https://www.hackerrank.com/challenges/game-of-throne-ii