You are given two strings, s and t. Find the shortest part of s (a substring) that contains every character of t, including repeats. For example, if t has two a, the part must have at least two a.
Return that shortest part. If no part of s works, return the empty string "". In the tests, the answer is always unique.
Examples
Example 1:
Input: s = "bbaac", t = "aba"
Output: "baa"
Explanation: The part "baa" has one b and two a. No shorter part works.
Example 2:
Input: s = "MnnoPMo", t = "Mo"
Output: "Mo"
Explanation: The last two characters "Mo" contain M and o. Capital and small letters are different.
Example 3:
Input: s = "abc", t = "cc"
Output: ""
Explanation: t needs two c, but s has only one, so the answer is empty.