438. 找到字符串中所有字母异位词

from collections import Counter
from typing import List


class Solution:
    def findAnagrams(self, s: str, p: str) -> List[int]:
        pc, l, res, sc = Counter(p), len(p), list(), Counter(s[:len(p)])

        if sc == pc:
            res.append(0)

        for i in range(l, len(s)):
            sc[s[i - l]] = sc.get(s[i - l]) - 1
            if sc[s[i - l]] == 0:
                sc.pop(s[i - l])
            sc[s[i]] = sc.get(s[i], 0) + 1

            if sc == pc:
                res.append(i - l + 1)

        return res