Given strings s and t, return the shortest substring of s that contains every character of t, including duplicates. If no such substring exists, return an empty string.
When an answer exists, it is guaranteed to be unique.
Examples
Example 1
- Input
- s = "ADOBECODEBANC", t = "ABC"
- Output
- "BANC"
Example 2
- Input
- s = "a", t = "a"
- Output
- "a"
Example 3
- Input
- s = "a", t = "aa"
- Output
- ""
- Why
- t needs two a's, but s only has one.
Constraints
1 <= s.length, t.length <= 10^5sandtcontain uppercase and lowercase English letters.