Given a string source and a string target, find the minimum window in source which will contain all the characters in target.
If there is no such window in source that covers all characters in target, return the emtpy string “”.
If there are multiple such windows, you are guaranteed that there will always be only one unique minimum window in source.
Challenge: time complexity of O(n).
Source target Solution
abc a a
abc ac abc
abcd ac abc
abcdecf acc abcdec