Given two strings A and B of lowercase letters, return true
if and only if we can swap two letters in A so that the result equals
B.
Example 1:
Input: A = "ab", B = "ba" Output: true
Example 2:
Input: A = "ab", B = "ab" Output: false
Example 3:
Input: A = "aa", B = "aa" Output: true
Example 4:
Input: A = "aaaaaaabc", B = "aaaaaaacb" Output: true
Example 5:
Input: A = "", B = "aa" Output: false
Note:
0 <= A.length <= 200000 <= B.length <= 20000A and B consist only of lowercase
letters.