202. Happy Number【leetcode】java，hashSet,演算法

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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

題意：

寫一個演算法來判斷一個數字是否“快樂”。
一個愉快的數字是由下面的流程定義的一個數字：從任何正整數開始，用它的數位平方代替數字，重複這個過程直到數字等於1（它將停留在哪裡），或者在一個不包括1的迴圈中迴圈。這個過程以1結尾的數字是快樂數字。
例子：19是一個快樂的數字。

 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 }

 

 

202. Happy Number【leetcode】java，hashSet,演算法