leetcode 389. Find the Difference 牛人用异或或者求和解决，很简单。

た入场券 2022-07-17 04:09 88阅读 0赞

### 389. Find the Difference ###

Question Editorial Solution

[My Submissions][]

*  Total Accepted: 7465
 *  Total Submissions: 14609
 *  Difficulty: Easy

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.

我的解法：利用hashmap进行记录

public class Solution {
    public char findTheDifference(String s, String t){
        Map map=new HashMap<Character,Integer>();
        for(int i=0;i<s.length();i++){
            if(!map.containsKey(s.charAt(i)))
                map.put(s.charAt(i),1);
            else{
                int temp = (int)map.get(s.charAt(i));
                map.put(s.charAt(i),++temp);
            }
        }
        for(int a=0;a<t.length();a++){
            if(!map.containsKey(t.charAt(a))){
                return t.charAt(a);
            }
            else{
                int temp = (int)map.get(t.charAt(a));
                temp--;
                if(temp<0)return t.charAt(a);
                map.put(t.charAt(a),temp);
            }
        }
        return ' ';
        }
    }

牛人解法：

java 用异或：

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

或者用求和，c:

char findTheDifference(char* s, char* t) {
        int sum1=0,sum2=0;
        for(;*s;s++)
            sum1+=*s;
        for(;*t;t++)
            sum2+=*t;
        return sum2-sum1;
    }

[My Submissions]: https://leetcode.com/problems/find-the-difference/submissions/