【朱迪的LeetCode刷题笔记】9. Palindrome Number #Easy #C

Judie

9. Palindrome Number #Easy

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 palindrome while 123 is not.


Example 1:

Input: x = 121
Output: true

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.

Example 4:

Input: x = -101
Output: false
 

Constraints:

-231 <= x <= 231 - 1
 

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

C

#include <limits.h>

bool isPalindrome(int x){
    if (x < 0) {
        return false;
    }
    if (x == 0) {
        return true;
    }
    int temp_x = x;
    int reverse_x = 0;
    while (temp_x) {
        if (reverse_x > (INT_MAX - (temp_x % 10)) / 10) {
            return x / 10 == reverse_x && x % 10 == temp_x;
        }
        reverse_x = (reverse_x * 10) + (temp_x % 10);
        temp_x = temp_x / 10;
    }
    return reverse_x == x;
}