202.Happy Number

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

代码：

import java.util.HashSet;
import java.util.Set;
public class Solution {
    public boolean isHappy(int n) {
    Set<Integer> set = new HashSet<Integer>();

//用set判断是否有循环，如果循环就退出
    while(!set.contains(n)){
    set.add(n);
    n = calcute(n);
    if(n==1)
    return true;
    }
    return false ;
    }

//计算每位数的平方和
    public int calcute(int n){
    int []a = new int[10];
         int i = 0 ;
         int result = 0 ;
        while(n>0){
      a[i] = n%10;
      n = n/10;
      i++;
      }
     
      for(int k=0 ;k<i;k++){
      result += a[k]*a[k] ;
      }
     return result ;
    }
}