9.palindrome-number.java

/*
 * @lc app=leetcode id=9 lang=java
 *
 * [9] Palindrome Number
 *
 * https://leetcode.com/problems/palindrome-number/description/
 *
 * algorithms
 * Easy (42.02%)
 * Likes:    1514
 * Dislikes: 1331
 * Total Accepted:    624.1K
 * Total Submissions: 1.4M
 * 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?
 *
 */
class Solution {
  public boolean isPalindrome(int x) {
    if (x < 0) {
      return false;
    }

    int origin = x;
    int reverse = 0;

    while (x != 0) {
      reverse = reverse * 10 + x % 10;
      x /= 10;
    }

    return origin == reverse;
  }
}