題目描述：

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?

程式碼如下：

class Solution {
public:
    bool isPalindrome(int x) {
        int revhalf=0;
        int slow=x,fast=x;
        //revhalf是將slow即x反轉一半後的值，然後將slow和revhalf比較
        if(x<0||(x>0&&x%10==0))return false;//如果最後一位為0也不可能為迴文數
        while(fast){
            revhalf=revhalf*10+slow%10;
            slow/=10;
            fast/=100;
        }
        //如果x是奇位數，則slow等於（revhalf/10）,如果slow是偶位數，則slow等於revhalf
        return slow==revhalf||slow==(revhalf/10);
    }
};