Description (leetcode)

Given an integer x, return true if x is a palindrome, and false otherwise.

Example 1:

Input: x = 121

Output: true

Explanation: 121 reads as 121 from left to right and from right to left.

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.

Constraints:

  • -2^31 <= x <= 2^31 - 1

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

submission

impl Solution {
    pub fn is_palindrome(x: i32) -> bool {
        let mut reverse = 0;
        let mut tmp = x;
        // if x is negative, it is not palindrome
        if x < 0 {
            return false;
        }
        // construct a reversed number
        while tmp > 0 {
            reverse = reverse * 10 + tmp % 10;
            tmp /= 10;
        }
        // by definition
        reverse == x
    }
}