76.py

import re
import collections
import itertools
import heapq
import bisect

class Solution:
    def minWindow(self, s: str, t: str) -> str:
        need = collections.Counter(t)
        missing = len(t)
        left = start = end = 0

        for right, char in enumerate(s, 1):
            missing -= need[char] > 0
            need[char] -= 1

            if missing == 0:

                while left < right and need[s[left]] < 0:
                    need[s[left]] += 1
                    left += 1

                if not end or right - left <= end - start:
                    start, end = left, right
                    
                # need[s[left]] += 1
                # missing += 1
                # left += 1

        return s[start:end]