Minimum Window Substring

Problem Given strings s and t, return the minimum window substring of s that contains all characters of t including multiplicity. Return "" if no such window exists.

Input / Output

• Input: strings s and t.
• Output: the minimum window substring, or "".

Constraints

• 1 ≤ |s|, |t| ≤ 10^5.
• s and t consist of uppercase and lowercase English letters.

Example

• s="ADOBECODEBANC", t="ABC" → "BANC"