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

Example 1:

Input: 121
Output: true
Example 2:

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:

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

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

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

上面是初始代码（运行时间184ms），后面是更改之后的代码（运行时间52ms）
利用回文数的性质，直接对其进行反向计算，如果出现溢出，肯定不会和源数据相同。
在开始计算之前进行特判即可
static int x = [](){
    std::ios::sync_with_stdio(false);
    std::cin.tie(NULL);
    std::cout.tie(NULL);
    return NULL;
}();
class Solution {
public:
    bool isPalindrome(int x) {
        if(x < 0 || (x%10 == 0 && x != 0)){
            return false;
        }
        int res = 0;
        int orign = x;
        while(x){
            res = res*10 + x%10;
            x /= 10;
        }
        return res == orign;
    }
};