class Solution:
    def checkInclusion(self, s1: str, s2: str) -> bool:

        #TC: O(len(s2))
        #SC: O(1)

        #Using two dicts as metrics to evaluate whether s1 and substring of s2 are permutating of each other

        Dict1 = [0]*26

        for char in s1:
            Dict1[ord(char) - ord('a')] += 1

        TotalLen = len(s1)

        Dict2 = [0]*26

        for i, char in enumerate(s2):
            Dict2[ord(char) - ord('a')] += 1

            if i >= TotalLen:
                Dict2[ord(s2[i - TotalLen]) - ord('a')] -= 1

            if Dict2 == Dict1:
                return True

        return False