LeetCode之Happy Number

1、题目

Write an algorithm to determine if a number is "happy".

A happy number is a number defined by the following process: Starting with any positive integer, replace the number by the sum of the squares of its digits, and repeat the process until the number equals 1 (where it will stay), or it loops endlessly in a cycle which does not include 1. Those numbers for which this process ends in 1 are happy numbers.

Example: 19 is a happy number

• 12 + 92 = 82
• 82 + 22 = 68
• 62 + 82 = 100
• 12 + 02 + 02 = 1

Credits:
Special thanks to @mithmatt and @ts for adding this problem and creating all test cases.

2、分析

这个题目每次会把每位的平方相加，然后循环这样，然后知道这个数字等于1为止，经过我们举例分析，如果不是快乐数最终或者中途出现这些数字，最後都会进入 4 → 16 → 37 → 58 → 89 → 145 → 42 → 20 → 4 的循环中

3、代码实现

  

   

    

     

    
    

     

      public class Solution {
     
    
   

    

     

    
    

     

       public boolean isHappy(int n) {
     
    
   

    

     

    
    

     

      		if (n <= 0)
     
    
   

    

     

    
    

     

       return false;
     
    
   

    

     

    
    

     

       int result = 0;
     
    
   

    

     

    
    

     

       while (n != 0) {
     
    
   

    

     

    
    

     

       int temp = n % 10;
     
    
   

    

     

    
    

     

       result += temp * temp;
     
    
   

    

     

    
    

     

       n = n / 10;
     
    
   

    

     

    
    

     

       }
     
    
   

    

     

    
    

     

       if (result == 1) 
     
    
   

    

     

    
    

     

       return true;
     
    
   

    

     

    
    

     

       else if (result == 4 || result == 16 || result == 37 || result == 58 || result == 89 || result == 145 || result == 42 || result == 20 )
     
    
   

    

     

    
    

     

       return false;
     
    
   

    

     

    
    

     

       else 
     
    
   

    

     

    
    

     

       return isHappy(result);
     
    
   

    

     

    
    

     

       }
     
    
   

    

     

    
    

     

      }
     
    
  
 

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原文链接：chenyu.blog.csdn.net/article/details/69788173