9. Palindrome Number

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9. Palindrome Number

Description

Given an integer x, return true if x is a palindrome, and false otherwise.

Example 1:

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Input: x = 121
Output: true
Explanation: 121 reads as 121 from left to right and from right to left.

Example 2:

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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:

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

Constraints:

  • -2^31<= x <= 2^31- 1

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

Hints/Notes

Solution

Language: C++

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class Solution {
public:
    bool isPalindrome(int x) {
        if (x < 0 || (x > 0 && x % 10 == 0)) {
            return false;
        }
        int reversed = 0;
        while (x > reversed) {
            int digit = x % 10;
            x /= 10;
            reversed = reversed * 10 + digit;
        }
        return reversed == x || reversed / 10 == x;
    }
};