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 04:09 208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:

  1. Input:
  2. s = "abcd"
  3. t = "abcde"
  5. Output:
  6. e
  8. Explanation:
  9. 'e' is the letter that was added.

我的解法：利用hashmap进行记录

  1. public class Solution {
  2. public char findTheDifference(String s, String t){
  3.     Map map=new HashMap<Character,Integer>();
  4.     for(int i=0;i<s.length();i++){
  5.         if(!map.containsKey(s.charAt(i)))
  6.             map.put(s.charAt(i),1);
  7.         else{
  8.             int temp = (int)map.get(s.charAt(i));
  9.             map.put(s.charAt(i),++temp);
  10.         }
  11.     }
  12.     for(int a=0;a<t.length();a++){
  13.         if(!map.containsKey(t.charAt(a))){
  14.             return t.charAt(a);
  15.         }
  16.         else{
  17.             int temp = (int)map.get(t.charAt(a));
  18.             temp--;
  19.             if(temp<0)return t.charAt(a);
  20.             map.put(t.charAt(a),temp);
  21.         }
  22.     }
  23.     return ' ';
  24.     }
  25. }

牛人解法：

java 用异或：

  1. public char findTheDifference_B(String s, String t) {
  2.     char c = 0;
  3.     for (int i = 0; i < s.length(); ++i) {
  4.         c ^= s.charAt(i);
  5.     }
  6.     for (int i = 0; i < t.length(); ++i) {
  7.         c ^= t.charAt(i);
  8.     }
  9.     return c;
  10. }

或者用求和，c:

  1. char findTheDifference(char* s, char* t) {
  2.     int sum1=0,sum2=0;
  3.     for(;*s;s++)
  4.         sum1+=*s;
  5.     for(;*t;t++)
  6.         sum2+=*t;
  7.     return sum2-sum1;
  8. }

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