202_happy_number.java

class Solution {
    public boolean isHappy(int n) {
        Set<Integer> set = new HashSet<>();
        int num = n;
        boolean ans = false;
        while (!set.contains(num)) {
            set.add(num);
            num = cal(num);
            if (num == 1) {
                ans = true;
                break;
            }
        }
        return ans;
    }

    public int cal(int n) {
        int ans = 0;
        int tmp = 0;
        while (n != 0) {
            tmp = n % 10;
            ans += tmp * tmp;
            n = n / 10;
        }
        return ans;
    }
}

/**
 * This is my personal record of solving Leetcode Problems. 
 * If you have any questions, please discuss them in [Issues](https://github.com/mengxinayan/leetcode/issues).
 * Copyright (C) 2020-2022  mengxinayan
 *
 * This program is free software: you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation, either version 3 of the License, or
 * (at your option) any later version.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program.  If not, see <http://www.gnu.org/licenses/>.
 */