Given strings *s* and *t*, return the minimum window in *s* which will contain all characters in *t*. If no such window, return empty string. (Sliding-window + hash).
Two lines: string s, then string t.
The minimum window substring.
Example 1:
Input:
s = "ADOBECODEBANC" t = "ABC"
Output:
BANC
Explanation:
"BANC" is the smallest window covering A, B, and C.