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）：

class Solution {
public:
    int reverse(int x) {
        long long res = 0 ;
        while(x){
            res = res*10 + x%10 ;
            x /= 10 ;
        }
        if (res < INT_MIN || res > INT_MAX)
            return 0 ;
        else
            return res ;
    }
};