leetcode-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

题意：按照上例，拆分整数，得到平方和，如果最后结果为1，停止；如果结果为以前存在的数（陷入无限循环），也停止；

code：

package leetcode;

import java.util.*;

public class HappyNumber {
    // 停止条件：要么sum=1；要么这些结果中包含了sum；
    //对每个数字进行解析，利用可变数组进行存储得到的结果，判断是否为1还是有循环？
    //while(true)的用法；
    public static boolean isHappy(int n) {
        /*
         * int res = 0; Map<Integer, ArrayList<Integer>> map = new HashMap<>();
         * // map.put(n, new ArrayList<>()); int sum = n; while (sum != 1) {
         * List arr = new ArrayList(); map.put(sum, new ArrayList<Integer>());
         * if (map.containsKey(sum)) return false; if (n <= 9) {
         * map.get(sum).add(n); } else { while (n > 9) { res = n % 10;
         * map.get(sum).add(res); n = n / 10; } } Iterator ite = new Iterator();
         * for (int i = 0; i < map.get(sum).size(); i++) { int tmp = (Integer)
         * map.get(sum).get(i); sum += tmp * tmp; }
         *
         * } return true;
         */
        /* Map<Integer,ArrayList<Integer>> map = new HashMap<>(); */
        List<Integer> arr = new ArrayList<>();
        int sum = 0;
        while (true) {
            sum += (n % 10) * (n % 10);   //只是对一个数字这样分析即可！！
            n = n / 10;
            if (n == 0) {
                if (arr.contains(sum))
                    return false;
                else if (sum == 1)
                    return true;
            arr.add(sum);
            n = sum;
            sum = 0;
            }
        }
    }
    public static void main(String[] args) {
        // TODO Auto-generated method stub
        System.out.println(isHappy(7));
    }
}