You are given an integer array population and a binary string protection of the same length. A city at index i is currently protected if protection[i] == '0' and unprotected if protection[i] == '1'.

You may optionally shift any protected city's marker one position to the left (i.e., shift a '0' one index earlier in the string). Each protection marker can be shifted at most once, and two markers cannot occupy the same position after shifting. ...