package com.hit.basmath.learn.hash_table;

import java.util.HashSet;
import java.util.Set;

/**
 * 202. Happy Number
 * <p>
 * Write an algorithm to determine if a number is "happy".
 * <p>
 * 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.
 * <p>
 * Example:
 * <p>
 * Input: 19
 * Output: true
 * <p>
 * Explanation:
 * 12 + 92 = 82
 * 82 + 22 = 68
 * 62 + 82 = 100
 * 12 + 02 + 02 = 1
 */
public class _202 {
    public boolean isHappy(int n) {
        Set<Integer> inLoop = new HashSet<Integer>();
        int squareSum, remain;
        while (inLoop.add(n)) {
            squareSum = 0;
            while (n > 0) {
                remain = n % 10;
                squareSum += remain * remain;
                n /= 10;
            }
            if (squareSum == 1) {
                return true;
            } else {
                n = squareSum;
            }
        }
        return false;
    }
}