438. Find All Anagrams in a String

class Solution:
    def findAnagrams(self, s: str, p: str) -> List[int]:
        # time O(S+P) space O(1)
        cntP = {}
        cntS = {}
        r = 0
        res = []
        for pp in p:
            if pp not in cntP:
                cntP[pp] = 1
            else:
                cntP[pp] += 1
        # [l,r] is current window
        for l in range(len(s)):
            while r < len(s) and r - l +1 <= len(p):
                if s[r] not in cntS:
                    cntS[s[r]] = 1
                else:
                    cntS[s[r]] += 1
                r += 1
            if cntS == cntP:
                res.append(l)
            cntS[s[l]] -= 1
            if cntS[s[l]] == 0 :
                cntS.pop(s[l])
        return res