Minimum Window Substring

Given two strings s and t, return the minimum window substring of s such that every character in t (including duplicates) is included in the window. If no such window exists, return "".

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Example 1

Input: s = "ADOBECODEBANC", t = "ABC"
Output: "BANC"
Explanation: "BANC" is the smallest substring of s that contains 'A', 'B', and 'C'.

Example 2

Input: s = "a", t = "a"
Output: "a"
Explanation: The entire string is the minimum window.

Example 3

Input: s = "a", t = "aa"
Output: ""
Explanation: Both 'a's from t must be in the window. Since s has only one 'a', no valid window exists.

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Constraints

• 1 <= s.length, t.length <= 10^5
• s and t consist of uppercase and lowercase English letters.