438. Find All Anagrams in a String

https://leetcode.com/problems/find-all-anagrams-in-a-string/

Python

from collections import Counter


class Solution:
    def findAnagrams(self, s: str, p: str) -> List[int]:
        if len(s) < len(p):
            return []

        count_s, count_p = Counter(), Counter(p)

        ans = []
        for i in range(len(s)):
            count_s[s[i]] += 1

            # Reach end, move left (i-len(p)) forward
            if i >= len(p):
                if count_s[s[i-len(p)]] == 1:
                    del count_s[s[i-len(p)]]
                else:
                    count_s[s[i-len(p)]] -= 1

            # All counts are the same
            if count_s == count_p:
                ans.append(i-len(p)+1)

        return ans