Leetcode - Buddy Strings Solution

Given two strings a and b, return true if you can swap two letters in a so the result is equal to b, otherwise, return false.

Swapping letters is defined as taking two indices i and j (0-indexed) such that i != j and swapping the characters at a[i] and a[j].

• For example, swapping at indices 0 and 2 in "abcd" results in "cbad".

Example 1:

Input: a = "ab", b = "ba"
Output: true
Explanation: You can swap a[0] = 'a' and a[1] = 'b' to get "ba", which is equal to b.

Example 2:

Input: a = "ab", b = "ab"
Output: false
Explanation: The only letters you can swap are a[0] = 'a' and a[1] = 'b', which results in "ba" != b.

Example 3:

Input: a = "aa", b = "aa"
Output: true
Explanation: You can swap a[0] = 'a' and a[1] = 'a' to get "aa", which is equal to b.

Example 4:

Input: a = "aaaaaaabc", b = "aaaaaaacb"
Output: true

Constraints:

• 1 <= a.length, b.length <= 2 * 104
• a and b consist of lowercase letters.

Solution in Python

class Solution:
    def buddyStrings(self, a: str, b: str) -> bool:
        diff = [(i,j) for i,j in zip(a,b) if i!=j]
        freq = Counter(a)
        if len(a) != len(b):
            return False
        if len(diff) == 2 and diff[0][0] == diff[1][1] and diff[0][1]==diff[1][0]:
            return True
        elif len(diff) == 0 and any(map(lambda x: x>1, freq.values())):
            return True
        else:
            return False