原题：
Reverse digits of an integer.
Example1: x = 123, return 321
Example2: x = -123, return -321
leetcode测试用例无语，超过int界限要求返回0。。。。。。。。。。。。。。
class Solution {
public:
int reverse(int x) {
long int result=0;
const int max = 0x7fffffff;
const int min = 0x80000000;
while(x!=0)
{
int pa=x%10;
result=result*10+pa;
if(result>max||result
