[LeetCode]Find the Difference

题目描述：

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.

题目大意：

给定两个字符串s和t，都只包含小写字母。

字符串t由字符串s打乱顺序并且额外在随机位置添加一个字母组成。

寻找t中新增的那个字母。

测试用例如题目描述。

解题思路：

分别统计s与t的字母个数，然后比对即可。若使用Python解题，可以使用collections.Dict。

Python代码：

class Solution(object):
    def findTheDifference(self, s, t):
        """
        :type s: str
        :type t: str
        :rtype: str
        """
        ds = collections.Counter(s)
        dt = collections.Counter(t)
        return (dt - ds).keys().pop()