Happy Number

浏览数：26 / 时间：2015年06月11日

https://leetcode.com/problems/happy-number/

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.

 1 import java.util.HashSet;
 2 import java.util.Set;
 3 
 4 public class Solution {
 5     public static boolean isHappy(int n) {
 6     if(n==1){return true;}
 7     Set<Integer>set=new HashSet();
 8     int result=0;
 9         while(result!=1){
10             result=0;
11             String x=n+"";
12             int len=x.length();
13             for(int i=0;i<len;i++){
14             char c=x.charAt(i);
15             result+=(c-‘0‘)*(c-‘0‘);
16             }
17             if(set.contains(result)){return false;}
18             set.add(result);
19             n=result;
20         }
21         return true;
22     }
23     public static void main(String[]args){
24     System.out.println(isHappy(19));
25     }
26 }