Most common substring of length X

Question

I have a string s and I want to search for the substring of length X that occurs most often in s. Overlapping substrings are allowed.

For example, if s=\"aoaoa\" and X=3

Answer 1

LZW algorithm does this

This is exactly what Lempel-Ziv-Welch (LZW used in GIF image format) compression algorithm does. It finds prevalent repeated bytes and changes them for something short.

LZW on Wikipedia