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.
A substring is a contiguous sequence of characters within the string.
Input: s = "ADOBECODEBANC", t = "ABC"
Explanation: The minimum window substring "BANC" includes 'A', 'B', and 'C' from string t.
Input: s = "a", t = "a"
Explanation: The entire string s is the minimum window.
Input: s = "a", t = "aa"
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.