LeetCode //C - 9. Palindrome Number

9. Palindrome Number

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

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:

• $-2^{31}<=x<=2^{31}-1$

From: LeetCode
Link: 9. Palindrome Number

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Solution:

Ideas：

• We first check if the number is negative. If it is, we return false.
• We then reverse the number. We use a long for the reversed number to handle cases where reversing the integer might cause an overflow.
• Finally, we compare the original number with the reversed number. If they are equal, the number is a palindrome, so we return true; otherwise, false.

Code:

bool isPalindrome(int x) {
    // Negative numbers are not palindromes
    if (x < 0) {
        return false;
    }

    int original = x;
    long reversed = 0; // Use long to avoid integer overflow

    // Reversing the number
    while (x != 0) {
        reversed = reversed * 10 + x % 10;
        x /= 10;
    }

    // Check if the original number is equal to its reverse
    return original == reversed;
}
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