LeetCode/com/zerroi/leetcode/Three20/IsHappy.java

package com.zerroi.leetcode.Three20;

import java.util.HashMap;
import java.util.Map;

public class IsHappy {
    public static void main(String[] args) {
        SolutionFirst solutionFirst = new SolutionFirst();
        boolean res = solutionFirst.isHappy(2);
        System.out.println("res = " + res);
    }
}

class SolutionFirst {
    public boolean isHappy(int n) {
        return isHappyHelper(n, new HashMap<>());
    }

    private boolean isHappyHelper(int n, Map<Integer, Integer> map) {
        if (n == 1) return true;

        int key = getNum(n);
        if (map.containsKey(key)) {
            return false;
        }

        map.put(key, 1);
        return isHappyHelper(key, map);
    }

    private int getNum(int n) {
        int sum = 0;
        while (n > 0) {
            int a = n % 10;
            n /= 10;
            sum += a * a;
        }
        return sum;
    }
}