9.palindrome-number.cpp

/*
 * @lc app=leetcode id=9 lang=cpp
 *
 * [9] Palindrome Number
 *
 * https://leetcode.com/problems/palindrome-number/description/
 *
 * algorithms
 * Easy (47.67%)
 * Likes:    2238
 * Dislikes: 1535
 * Total Accepted:    912.8K
 * Total Submissions: 1.9M
 * Testcase Example:  '121'
 *
 * Determine whether an integer is a palindrome. An integer is a palindrome
 * when it reads the same backward as forward.
 *
 * Example 1:
 *
 *
 * Input: 121
 * Output: true
 *
 *
 * Example 2:
 *
 *
 * Input: -121
 * Output: false
 * Explanation: From left to right, it reads -121. From right to left, it
 * becomes 121-. Therefore it is not a palindrome.
 *
 *
 * Example 3:
 *
 *
 * Input: 10
 * Output: false
 * Explanation: Reads 01 from right to left. Therefore it is not a
 * palindrome.
 *
 *
 * Follow up:
 *
 * Coud you solve it without converting the integer to a string?
 *
 */

// @lc code=start
#include <vector>
using std::vector;

class Solution {
   public:
    bool isPalindrome(int x) {
        if (x < 0 || x % 10 == 0 && x != 0) {
            return false;
        }

        int revertedNum{0};

        while (x > revertedNum) {
            revertedNum = revertedNum * 10 + x % 10;
            x = x / 10;
        }

        return x == revertedNum || x == revertedNum / 10;
    }
};
// @lc code=end