LeetCode in Kotlin

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

class Solution {
    fun isPalindrome(x: Int): Boolean {
        if (x < 0) return false
        var rev = 0
        var localX = x
        while (localX > 0) {
            rev *= 10
            rev += localX % 10
            localX /= 10
        }
        return rev == x
    }
}

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