Leetcode 438. Find All Anagrams in a String

class Solution:
    def findAnagrams(self, s: str, p: str) -> List[int]:
        stat = collections.Counter(p)
        n = len(p)
        stat['length'] = n
        result = []
        subs = collections.defaultdict(int)
        for index, ch in enumerate(s):
            if ch in stat:
                subs[ch] += 1
                subs['length'] += 1
            else:
                subs = collections.defaultdict(int)
                continue
            if subs['length'] == stat['length']:
                if stat == subs:
                    result.append(index - n + 1)
                subs[s[index - n + 1]] -= 1
                subs['length'] -= 1
        return result