"""
76. Minimum Window Substring
Difficulty: Hard
https://leetcode.com/problems/minimum-window-substring/

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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 "".

The testcases will be generated such that the answer is unique.

 

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.

 

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

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