import java.util.HashSet;

import java.util.Set;

/*

Write an algorithm to determine if a number n 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.

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.

Return true if n is a happy number, and false if not.

Example 1:

Input: n = 19

Output: true

Explanation:

12 + 92 = 82

82 + 22 = 68

62 + 82 = 100

12 + 02 + 02 = 1

Example 2:

Input: n = 2

Output: false

*/

public class LeetCode202_2 {

static int sumOfPow(int n){

int ps=0;

while(n>0){

int rem = n%10;

ps +=rem*rem;

n/=10;

}

return ps;

}

static public boolean isHappy_2(int n) {

Set<Integer> powSum = new HashSet<>();

while(true){

int sum = sumOfPow(n);

if(sum==1)return true;

n=sum;

if(powSum.contains(n))return false;

powSum.add(n);

}

}

public static void main(String[] args) {

System.out.println(isHappy_2(37));

}

}