Find All Anagrams in a String

Given two strings s and p, return an array of all the start indices of p's anagrams in s. You may return the answer in any order.

An Anagram is a word or phrase formed by rearranging the letters of a different word or phrase, typically using all the original letters exactly once.

Example 1:

Input: s = "cbaebabacd", p = "abc"
Output: [0,6]
Explanation:
The substring with start index = 0 is "cba", which is an anagram of "abc".
The substring with start index = 6 is "bac", which is an anagram of "abc".

Example 2:

Input: s = "abab", p = "ab"
Output: [0,1,2]
Explanation:
The substring with start index = 0 is "ab", which is an anagram of "ab".
The substring with start index = 1 is "ba", which is an anagram of "ab".
The substring with start index = 2 is "ab", which is an anagram of "ab".

Constraints:

• 1 <= s.length, p.length <= 3 * 104
• s and p consist of lowercase English letters.

SOLUTION:

class Solution:
    def findAnagrams(self, s: str, p: str) -> List[int]:
        np = len(p)
        ns = len(s)
        op = []
        if np > ns:
            return op
        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:
                op.append(i)
            sctr[ord(s[i]) - ord('a')] -= 1
            sctr[ord(s[i + np]) - ord('a')] += 1
            i += 1
        if pctr == sctr:
            op.append(i)
        return op