9. Palindrome Number

2019-03-28

9. Palindrome Number

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

Example 1:

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Input: 121
Output: true

Example 2:

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Input: -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:

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Input: 10
Output: false
Explanation: Reads 01 from right to left. Therefore it is not a palindrome.

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

Code:

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class Solution(object):
    def isPalindrome(self, x):
        """
        :type x: int
        :rtype: bool
        """
        if x < 0 or (x != 0 and x%10 == 0):
            return False

        y = 0
        while x > y:
            y = y*10 + x%10
            x =  x // 10
        return x == y or y // 10 == x

If we solve it with converting the integer to a string

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class Solution:
    def isPalindrome(self, x: int) -> bool:
        return str(x) == str(x)[::-1]
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