---
title: '76. Minimum Window Substring'
description: Given two strings s and t of lengths m and n respectively, return the minimum window substring of s such that every character in t (including duplicates) is included in the window. If there is no such substring, return the empty string ""
icon: dot
topics:
  - { name: "Hash Table", slug: "hash-table" }
  - { name: "String", slug: "string" }
  - { name: "Sliding Window", slug: "sliding-window" }
issue: "https://github.com/prdlk/leetcode/issues/57"
sidebar:
  label: 'Minimum Window Substring'
  badge: 'Hard'
---

::::warning
Could you find an algorithm that runs in O(m + n) time?
::::

### Example 1:
- Input: `s = "ADOBECODEBANC", t = "ABC"`
- Output: `"BANC"`
- Explanation: The minimum window substring "BANC" includes 'A', 'B', and 'C' from string `t`.

### Example 2:
- Input: `s = "a", t = "a"`
- Output: `"a"`
- Explanation: The entire string `s` is the minimum window.

### Example 3:
- Input: `s = "a", t = "aa"`
- Output: `""`
- Explanation: Both 'a's from `t` must be included in the window. Since the largest window of `s` only has one 'a', return empty string.

### Constraints:

- `m == s.length`
- `n == t.length`
- `1 <= m, n <= 10^5`
- `s` and `t` consist of uppercase and lowercase English letters.

## Solution

```py
class Solution:
    def minWindow(self, s: str, t: str) -> str:
```