Minimum Window Substring

🔍 Problem Statement: 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.

Examples

🔹 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', the output is an 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?