202. Happy Numberleetcodejava，hashSet,算法

Posted 2020-10-03 皓浩浩皓

202. Happy Number

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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

题意：

写一个算法来判断一个数字是否“快乐”。
一个愉快的数字是由下面的过程定义的一个数字：从任何正整数开始，用它的数字的平方代替数字，重复这个过程直到数字等于1（它将停留在哪里），或者在一个不包括1的循环中循环。这个过程以1结尾的数字是快乐数字。
例子：19是一个快乐的数字。

 1 public class Solution {
 2     private int getHappyNumber(int n){
 3         int sum=0;
 4         while(n!=0){
 5             sum+=(n%10)*(n%10);
 6             n=n/10;
 7         }
 8         return sum;
 9     }
10     public boolean isHappy(int n) {
11         HashSet<Integer> hash=new HashSet<Integer>();
12         while(n!=1){
13             if(hash.contains(n))
14                 return false;
15             else{
16                 hash.add(n);
17                 n=getHappyNumber(n);
18             }
19         }
20         return true;
21     }
22 }