LeetCode笔记--202Happy Number

1 题目描述

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

链接地址：https://leetcode.com/problems/happy-number/

2 解决方案

java代码如下：

public class Solution {
    public boolean isHappy(int n) {
        int result = 0;
	ArrayList<Integer> list = new ArrayList<Integer>();
    	boolean isLucky = false;
    	if (n <= 0) {
			return isLucky;
		}
		while (true) {
			int sum = 0;
			int num = n;
			while (num > 0) {
				int temp = num%10;
				num = (num -temp)/ 10;
				sum = sum  + temp * temp ;
			}

			result = sum;

			if (result ==1 ) {
				isLucky = true;
				break;
			}
			else if(list.contains(result)) {
				isLucky = false;
				break;
			}else {
				n = result;
				list.add(result);
			}

		}
		return isLucky;
    }
}