code only works with 3 digits

This code for finding the binary representation of a number works if I type a number of 3 digits but if i type a number like 3427 , it doesn't ...
I use Dev-++ , I have tried to debug and apparently the problem is on the line after while , perhaps the ze[u] .

Code:

---

#include <iostream>
using namespace std;
int main()
{
 long x,z,n,y=0,u;
 long ze[y];
 
cout<<"write an integer : ";
cin>>x;
    for(n=x;n>0;n/=2){
    z=n%2; 
    cout<<z<<',';ze[y]={z}; y++;               
    }
    cout<<"  The last digit  is the first digit\n of the binary representation of "<<x<<endl<<endl;
    cout<<" Now , the right order : "<<endl;
    u=y-1;
    while (u>=0){
          cout<<ze[u]<<",";u--;
          }
    char zs;cin>>zs;
}

---

Knock out that array declaration with a variable as the size.

This works:

Code:

---

#include <iostream>
using namespace std;
int main()
{
 long x,z,n,y,u;
 y = 0;
 long ze[100];
 
cout<<"Write an integer : ";
cin>>x;
    for(n = x; n > 0; n /= 2){
    z = n % 2; 
    cout << z;
    ze[y]=z;
    y++;               
    }
    cout<<"  The last digit  is the first digit\n of the binary representation of "<<x<<endl<<endl;
    cout<<" Now , the right order : "<<endl;
    u=y-1;
    while (u>=0){
          cout<<ze[u];
          u--;
          if ((u+1) % 4 == 0)
            cout << " ";
          }
          }
    char zs;
    cin>>zs;
}

---

You're going out of bounds on your index, the program is trying to access memory that doesn't belong to it, and windows is giving it a spanking.

Thanks , it is more pleasant like that .

As a critique on the output, I don't understand why you even bother showing it backwards, it's much nicer looking like this.

Code:

---

#include <iostream>
using namespace std;
int main()
{
 long x,z,n,y,u;
 y = 0;
 long ze[100];
 
cout << "Write an integer: ";
cin >> x;
cin.ignore();
    for(n = x; n > 0; n /= 2){
    z = n % 2;
    ze[y] = z;
    y++;               
    }
    cout<<"Binary Representation: "<<endl;
    u = y - 1;
    while (u >= 0){
          cout << ze[u];
          u--;
          if ((u+1) % 4 == 0)
            cout << " ";
          }
    cin.get();
}

---

Sample Output:

Code:

---

Write an integer: 364365
Binary Representation:
101 1000 1111 0100 1101

---

The simple reason was that i didnt know how to dispay it rightward on the screen .
The spaces between every 4 digits also make the result easier to read .