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9. Palindrome Number

Difficulty Topics

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

palindrome-number.py
class Solution:
    def isPalindrome(self, x: int) -> bool:
        x = str(x)
        i, j = 0, len(x)-1

        while i < j and x[i] == x[j]:
            i += 1
            j -= 1

        return i >= j