[Leetcode] 202. Happy Number

202. 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

Credits:Special thanks to @mithmatt and @ts for adding this problem and creating all test cases.

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