leetcode Happy Number 202

標籤：leetcode happy numbe

Happy Number  Total Accepted: 11462  Total Submissions:  35743

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

Hide tags  HashTable Math思路：多次使用自訂的求平方和函數， 關鍵在於分離給定數的各個位置上的數，通常使用 s=n%10 ,n=n/10 方法進行數文書處理
代碼如下：

public  boolean isHappy(int n){int sum=powsum(n);while(sum>9){//不滿足條件時，多次調用sum=powsum(sum);}if(sum==1){return true;}return false;}private int powsum(int n){int sum=0;//使用while迴圈while(n!=0){//分離數各個位置上的數int s=n%10;//求平方和，其中Math.pow(x,y) 意思為x的y次冪sum=(int) (sum+Math.pow(s, 2));n=n/10;}return sum;}

補充：可以使用HashTable 對每一次powsum返回的值進行記錄，如果HashTable中已經有記錄，則說明進入了死迴圈，直接返回false, 

leetcode Happy Number 202