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

Posted 2022-12-05 厚积_薄发

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;