70-Stack--LC389找不同

ord()将字符转换成ASCII
chr()将ASCII转换成字符

class Solution(object):
    def findTheDifference(self, s, t):
        """
        :type s: str
        :type t: str
        :rtype: str
        """
        # 1.异或 0^N = N , N^N = 0
        res = 0
        for i in s+t:
            res ^= ord(i)
        return chr(res)
        # 2.用栈
        if len(s) == 0:
            return t
        res = [0] * 26
        # s中有就存-1，t中有就存+1，这样就可以使用一个列表来完成任务
        for i in s:
            i = ord(i) - 97
            res[i] = res[i] - 1
        for j in t:
            j = ord(j) - 97
            res[j] = res[j] + 1
        for t in res:
            if t == 1:
                return chr(res.index(t)+97)