算法题之substring

Sliding window for substring

Reference:https://leetcode.com/problems/find-all-anagrams-in-a-string/discuss/92007/Sliding-Window-algorithm-template-to-solve-all-the-Leetcode-substring-search-problem.

Problem: https://leetcode.com/problems/find-all-anagrams-in-a-string/ -> write code with sliding window for this problem