>Take a string, for example "ABCCABC" and count the number of times each 3 character substring occurs. In this case the answer would be 2xABC 1xBCC 1xCCA 1xCAB.

>Take a string, for example "ABCCABC" and count the number of times each 3 character substring occurs. In this case the answer would be 2xABC 1xBCC 1xCCA 1xCAB. Can be done in O(n) time with a hash table.