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.

本题的解法很类似single number，由于两个str只有一个字母不同。所以可以用xor。注意使用ord 和 chr 对于char和int之间进行转换。

class Solution(object):
    def findTheDifference(self, s, t):
        """
        :type s: str
        :type t: str
        :rtype: str
        """
        ans = 0
        for x in s:
            ans ^= ord(x)
        for y in t:
            ans ^= ord(y)
        return chr(ans)

 

解法二是使用collections.Counter

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()