[LeetCode 202]Happy Number

题目链接：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

public class Solution {    public boolean isHappy(int n) {    Set<Integer> s = new HashSet<Integer>();    while(n != 1) {    int sum = 0;    while(n != 0) {    int mod = n % 10;            sum += mod * mod;            n /= 10;    }    if(s.contains(sum))    return false;    s.add(n = sum);        }    return true;         }}