[leedcode 202] 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
    public class Solution {
        public boolean isHappy(int n) {
            //用一个set记录所有计算过的n,若出现重复(循环),返回false,若n为1,返回true;
            Set<Integer> set=new HashSet<Integer>();
            while(n!=1){
                int sum=0;
                while(n!=0){
                    sum+=(n%10)*(n%10);
                    n/=10;
                }
                if(set.contains(sum)) return false;
                set.add(sum);
                n=sum;
            }
            return true;
        }
    }

     

posted @ 2015-08-03 21:54  ~每天进步一点点~  阅读(126)  评论(0编辑  收藏  举报