s0009_palindrome_number

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:

• -231 <= x <= 231 - 1

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

Solution

/**
 * @param {number} x
 * @return {boolean}
 */
var isPalindrome = function (x) {
    if (x < 0) {
        return false
    }

    let rev = 0
    let localX = x

    while (localX > 0) {
        rev = rev * 10 + (localX % 10)
        localX = Math.floor(localX / 10)
    }

    return rev === x
}

export { isPalindrome }