leetcode 389. Find the Difference

/*
leetcode 389. Find the Difference

Given two strings s and t which consist of only lowercase letters.

String t is generated by random shuffling string s and then add one more letter at a random position.

Find the letter that was added in t.

Example:

Input:
s = "abcd"
t = "abcde"

Output:
e

Explanation:
'e' is the letter that was added.
*/

#include <string>
#include <iostream>

using namespace std;

class Solution {
public:
    char findTheDifference(string s, string t) 
    {
        if (s.size() == 0)
            return t[0];
        int res = 0;
        for (auto c : s)
            res ^= c;
        for (auto c : t)
            res ^= c;

        return static_cast<char>(res);
    }
};


void test()
{
    string s("abc");
    string t("bacf");
    Solution sol;
    cout << sol.findTheDifference(s, t) << endl;
}

int main()
{
    test();
}