leetcode 202. Happy Number

快乐数判断算法

最新推荐文章于 2021-08-15 11:22:37 发布

转载最新推荐文章于 2021-08-15 11:22:37 发布 · 401 阅读

文章标签：

#leetcode #算法

Leetcode 专栏收录该内容

48 篇文章

订阅专栏

本文介绍了一种用于判断一个正整数是否为快乐数的算法。快乐数是指通过反复替换该数为它每个位数的平方和，最终得到1的数字。文章提供了一个具体的示例，演示了如何使用Java实现这一过程，并附带完整的代码。

题目

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

解

public class Solution {
       public boolean isHappy(int n) {

        if(n<=0)   return false;

        long ln=n;
        Set<Long> iS=new HashSet<Long>();

        while(ln<=Integer.MAX_VALUE){
            if(iS.contains(ln))
                return false;
            else
                iS.add(ln);

            ln=digitsSqures(ln);
            if(ln==1) return true;
        }

        return false;

    }

    long digitsSqures(long ln){

        long ret=0;
        while(ln>0){
            ret+=Math.pow(ln%10, 2);
            ln=ln/10;       
        }       
        return ret;

    }
}