Leetcode 889 Solution

This article provides solution to leetcode question 889 (buddy-strings)
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https://leetcode.com/problems/buddy-strings

Solution

class Solution(object):
    def buddyStrings(self, A, B):
        """
        :type A: str
        :type B: str
        :rtype: bool
        """
        if len(A) != len(B):
            return False

        cnt = collections.defaultdict(int)

        s1 = set()
        s2 = set()
        for ch1, ch2 in zip(A, B):
            if ch1 != ch2:
                s1.add(ch1)
                s2.add(ch2)
            cnt[ch1] += 1

        if len(s1) == 0:
            return True if [v for v in cnt.values() if v > 1] else False
        elif len(s1) == 2:
            return s1 == s2
        else:
            return False