Palindrome Number

11 Mar, 2021

Problem

Determine whether an integer is a palindrome. An integer is a palindrome when it reads the same backward as forward.

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

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:

-231 <= x <= 231 - 1

My Solution

success

const isPalindrome = (x) => {
	if (x < 0) return false;
	let reverseX = parseInt(x.toString().split('').reverse().join(''));
	return reverseX === x;
};

success

const isPalindrome = (x) => {
	if (x < 0 || (x % 10 === 0 && x !== 0)) return false;
	let rev = 0;
	let origin = x;
	while (origin > 0) {
		rev = rev * 10 + (origin % 10);
		origin = ~~(origin / 10);
	}
	return x === rev;
};