leetcode Reverse Integer

Reverse digits of an integer.

Example1: x = 123, return 321
Example2: x = -123, return -321

class Solution {
public:
    int reverse(int x) {
        bool flag = x < 0 ?0:1;
        ostringstream os;
        os<>n;
        if (!flag) n = -n;
        if (n == 2147483647 || n == -2147483647){
            return 0;
        }
        return (int)n;
    }
};