567 Permutation in String

Given two strings s1 and s2, return true if s2 contains a permutation of s1, or false otherwise.

In other words, return true if one of s1’s permutations is the substring of s2.

Example 1:

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

Example 2:

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

Constraints:

  • 1 <= s1.length, s2.length <= 104
  • s1 and s2 consist of lowercase English letters.
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class Solution:
    def checkInclusion(self, s1: str, s2: str) -> bool:
        l1 = [0]*26
        l2 = [0]*26
        for x in s1:
            l1[ord(x) - ord('a')] += 1
        
        for i in range(len(s2)):
            l2[ord(s2[i]) - ord('a')] += 1
            if i >= len(s1):
                l2[ord(s2[i-len(s1)]) - ord('a')] -= 1
            if l1 == l2:
                return True
        return False