9-palindrome-number

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Description

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 a palindrome while 123 is not.

 

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:

• -231 <= x <= 231 - 1

 

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

Solution(Python)

class Solution:
    def isPalindrome(self, x: int) -> bool:
        if x < 0 or (
            x > 0 and x % 10 == 0
        ):  # if x is negative, return False. if x is positive and last digit is 0, that also cannot form a palindrome, return False.
            return False

        result = 0
        while x > result:
            result = result * 10 + x % 10
            x = x // 10

        return True if (x == result or x == result // 10) else False