Return true if two strings match with only one swap.

To determine if two strings can be made equal by swapping exactly one pair of characters, first check that the strings have the same length. Then iterate through the strings and record the indices where the characters differ. If there are exactly two mismatched positions i and j, check whether swapping the characters at these positions in the first string makes it equal to the second string. If so, return true; otherwise return false. If the number of mismatches is not exactly two, return false. This algorithm runs in O(n) time and O(1) additional space, where n is the length of the strings.