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.lengthn == t.length1 <= m, n <= 105s and t consist of uppercase and lowercase English letters.Follow up: Could you find an algorithm that runs in O(m + n) time?