Leetcode 0389 Find the Difference

Problem statement

https://leetcode.com/problems/find-the-difference/

Solution

One solution is just to use counters and then find the difference, time complexity is O(n), space is (26) number of letters.

Complexity

Code

class Solution:
    def findTheDifference(self, s, t):
        return list((Counter(t) - Counter(s)).keys())[0]

Remark

There is another O(1) space solution, using bit manipulations: just evaluate bit-wise xor for all symbols in two words and you answer will be exactly symbol we are looking for.