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.

SOLUTION:

class Solution:
    def checkInclusion(self, p: str, s: str) -> bool:
        np = len(p)
        ns = len(s)
        if np > ns:
            return False
        pctr = [0] * 26
        for c in p:
            pctr[ord(c) - ord('a')] += 1
        sctr = [0] * 26
        for i in range(np):
            sctr[ord(s[i]) - ord('a')] += 1
        i = 0
        while i < ns - np:
            if pctr == sctr:
                return True
            sctr[ord(s[i]) - ord('a')] -= 1
            sctr[ord(s[i + np]) - ord('a')] += 1
            i += 1
        if pctr == sctr:
            return True
        return False