9. 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.

 

思路：两个字符串中只有一个字符只出现了一次，所以等价于那个在一个数组中找出只出现一次的那个数的问题。利用异或操作。C++中可以用”[]”运算符索引string对象对应位置的字符。