Hi, here's your problem today. This problem was recently asked by AirBNB:

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
Here's a starting point:

<pre lang=py>
class Solution:
  def buddyStrings(self, A, B):
    # Fill this in.

print Solution().buddyStrings('aaaaaaabc', 'aaaaaaacb')
# True
print Solution().buddyStrings('aaaaaabbc', 'aaaaaaacb')
# False
</pre>