LeetCode-in-All

9. Palindrome Number

Easy

Given an integer x, return true if x is palindrome integer.

An integer is a palindrome when it reads the same backward as forward. For example, 121 is palindrome while 123 is not.

Example 1:

Input: x = 121

Output: true

Example 2:

Input: x = -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: x = 10

Output: false

Explanation: Reads 01 from right to left. Therefore it is not a palindrome.

Example 4:

Input: x = -101

Output: false

Constraints:

Follow up: Could you solve it without converting the integer to a string?

Solution

public class Solution {
    public bool IsPalindrome(int x) {
        if (x < 0) {
            return false;
        }
        int rev = 0;
        int localX = x;
        while (localX > 0) {
            rev *= 10;
            rev += localX % 10;
            localX /= 10;
        }
        return rev == x;
    }
}