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.

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

Output:
e

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

     用xor!!!

class Solution {
public:
    char findTheDifference(string s, string t) {
        int ans = 0;
        for(int i = 0; i < s.size(); i++)
        {
            ans ^= s[i] ^ t[i];
        }
        ans ^= t[s.size()];
        return ans;
    }
};