Leetcode 567 - Permutation in String

Prompt: Given two strings s1 and s2, return true if s2 contains the permutation of s1. In other words, one of s1’s permutations is the substring of s2.

Example:

Input: s1 = "ab", s2 = "eidbaooo"
Output: true
Explanation: s2 contains one permutation of s1 ("ba").

Input: s1 = "ab", s2 = "eidboaoo"
Output: false

Solution: The solution for this problem is a sliding window. The condition for the sliding window is that it should be the length of string s1 and all characters in the sliding window should have the same frequency of all the characters in s1. The runtime is O(n).