### minWindow 
import math
from math import inf
from collections import Counter
from typing import *
def f_gold(s: str, t: str) -> str:
    ans = ''
    m, n = len(s), len(t)
    if m < n:
        return ans
    need = Counter(t)
    window = Counter()
    i, cnt, mi = 0, 0, float('inf')
    for j, c in enumerate(s):
        window[c] += 1
        if need[c] >= window[c]:
            cnt += 1
        while cnt == n:
            if j - i + 1 < mi:
                mi = j - i + 1
                ans = s[i : j + 1]
            c = s[i]
            if need[c] >= window[c]:
                cnt -= 1
            window[c] -= 1
            i += 1
    return ans