7. Reverse Integer

Given a 32-bit signed integer, reverse digits of an integer.

Example 1:

Input: 123
Output:  321

Example 2:

Input: -123
Output: -321

Example 3:

Input: 120
Output: 21

Note:
Assume we are dealing with an environment which could only hold integers within the 32-bit signed integer range. For the purpose of this problem, assume that your function returns 0 when the reversed integer overflows.

反转一个整数，溢出时返回0

C++（26ms）：

 1 class Solution {
 2 public:
 3     int reverse(int x) {
 4         long long res = 0 ;
 5         while(x){
 6             res = res*10 + x%10 ;
 7             x /= 10 ;
 8         }
 9         if (res < INT_MIN || res > INT_MAX)
10             return 0 ;
11         else
12             return res ;
13     }
14 };