从零开始的LC刷题(81): Find the Difference

原题：

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.

找到t中多出来的字母，顺序是乱序，看到这道题我一下子就想起来了上次那个按位异或数字找一个数字的题，详细说明可以参考这个：

https://blog.csdn.net/cyr429/article/details/90640938

结果：

Success

Runtime: 0 ms, faster than 100.00% of C++ online submissions for Find the Difference.

Memory Usage: 8.8 MB, less than 94.22% of C++ online submissions for Find the Difference.

代码：

class Solution {
public:
    char findTheDifference(string s, string t) {
        char res=t.back();
        for(int i=0;i