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.

判断一个int型数是不是回文数。
这道题很简单，方法很多，但有个比较好的方法就是翻转一半长度比较是否相等，这样做不仅速度快而且不用考虑越界这类烦人的问题。

 1 public class Solution {
 2     public bool IsPalindrome(int x) {
 3         if (x < 0 || (x % 10 == 0 && x != 0))
 4         {
 5             return false;
 6         }
 7         int p = 0, i = 0;
 8         while (x >= 0)
 9         {
10             p = p * 10 + x % 10;
11             if (p == x) { return true; }
12             x /= 10;
13             if (p == x) { return true; }
14             i++;
15             if (x / (int)Math.Pow(10, i) == 0)
16             {
17                 break;
18             }
19         }
20         return false;
21     }
22 }