389. Find the Difference*-优快云博客

本文介绍了一种找出已知字符串在经过随机排列并添加一个新字母后的具体新增字母的方法。通过对比两个字符串的ASCII值之和的差异，可以高效地确定新增的字母。文章提供了几种不同的Python实现方案，包括使用异或操作、计数器工具和排序比较等方法。

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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.

My code:

class Solution(object):
    def findTheDifference(self, s, t):
        """
        :type s: str
        :type t: str
        :rtype: str
        """
        if len(s)==0:
            return t[0]
        
        sNum = [ord(i) for i in s]
        tNum = [ord(i) for i in t]
        sNum.sort()
        tNum.sort()
        for i in range(len(sNum)):
            if sNum[i]!=tNum[i]:
                return chr(tNum[i])
        return chr(tNum[i+1])

Another idea：

class Solution(object):
    def findTheDifference(self, s, t):
        """
        :type s: str
        :type t: str
        :rtype: str
        """
        c=0
        for i in range(len(s)):
          c ^=ord(s[i])
          c ^=ord(t[i])
        c ^=ord(t[len(t)-1])
        return chr(c)

Reference

class Solution(object):
    def findTheDifference(self, s, t):
        return chr(reduce(operator.xor, map(ord, s + t)))

class Solution(object):
    def findTheDifference(self, s, t):
        return list((collections.Counter(t) - collections.Counter(s)))[0]

class Solution(object):
    def findTheDifference(self, s, t):
        s, t = sorted(s), sorted(t)
        return t[-1] if s == t[:-1] else [x[1] for x in zip(s, t) if x[0] != x[1]][0]

Note: map,reduce, zip