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

#include<iostream> 
#include<windows.h> 
using namespace std; 
 
int reverse(int x) { 
    int num = 0; 
    while (x != 0) 
    { 
      int tail = x % 10; 
      int newnum = num * 10 + tail; 
      if ((newnum - tail) / 10 != num) 
      { 
        return 0; 
      } 
      num = newnum; 
      x /= 10; 
    } 
    return num; 
} 

int main() 
{ 
  cout << reverse(123) << endl; 
  cout << reverse(-123) << endl; 
  cout << reverse(1000000003) << endl; 
 
  system("pause"); 
  return 0; 
}