389 Find the Difference

Leetcode

You are given two strings s and t.

String t is generated by random shuffling string s and then add one more letter at a random position.

Return the letter that was added to t.

Example 1:

Input: s = "abcd", t = "abcde" Output: "e" Explanation: 'e' is the letter that was added. Example 2:

Input: s = "", t = "y" Output: "y"

可以用一个 int[26] 数组储存每个字符出现多少次。但还有更简单的方法：计算两个字符串所有 char 的和，差值为多出的字符。

public char findTheDifference(String s, String t) {
    char c=0;
    for(int i=0;i<s.length();++i){
        c+=t.charAt(i)-s.charAt(i);
    }
    return c+=t.charAt(t.length()-1);
}

class Solution {
public:
    char findTheDifference(string s, string t) {
        char c=0;
        for(int i=0;i<s.length();++i){
            c+=t[i]-s[i];
        }
        return c+t[t.length()-1];
    }
};

class Solution:
    def findTheDifference(self, s: str, t: str) -> str:
        total = 0
        for i in range(len(s)):
            total += ord(t[i]) - ord(s[i])
        return chr(total + ord(t[-1]))