859. Buddy Strings

Easy

Given two strings s and goal, return true if you can swap two letters in s so the result is equal to goal, 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 s[i] and s[j].

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

Solution

class Solution:
    def buddyStrings(self, s: str, goal: str) -> bool:
        if len(s) != len(goal):
            return False

        if s == goal:
            # need to find a duplicate character to swap
            seen = set()
            for a in s:
                if a in seen:
                    return True
                seen.add(a)
            return False

        pairs = []
        for a, b in zip(s, goal):
            if a != b:
                pairs.append((a, b))

        if len(pairs) != 2:
            return False

        if pairs[0] == pairs[1][::-1]:
            return True

        return False