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 store integers within the 32-bit signed integer range: [−231, 231 − 1]. For the purpose of this problem, assume that your function returns 0 when the reversed integer overflows.

//C/C++中常量INT_MAX和INT_MIN分别表示最大、最小整数，定义在头文件limits.h中

class Solution {
public:
    //7.反转整数
    int reverse(int x){
        long result = 0;
        //如-1230变成-321
        //从个位往前每次乘以10加到结果上去，这样不需要考虑正负号
        while(x != 0){
            result = result*10 + x%10;
            x /= 10;
        }
        return (result>INT_MAX || result <INT_MIN)?0:result;//超过上下限返回0
    }
};