double numbers in columns of same width

#include <cstdlib>
#include <iostream>
#include <iomanip>
#include <sstream>

 double string_to_double( const std::string& s )
 {
   std::istringstream i(s);
   double x;
   if (!(i >> x))
     return 0;
   return x;
 }
using namespace std;

int main()
{
    double TAB[1000];
    int max_length=0;
    int liczba=0;
    string liczby;
    cout << "How many numbers are you inputting into array: ";
    cin >> liczba;
    for (int a=0; a<=liczba; a++)
    {
        cin >> liczby;
        if (liczby.length() > max_length){max_length=liczby.length();}
        TAB[a]=string_to_double (liczby);
    }
    cout << endl;

    for (int a=0; a<=liczba; a++)
    {

    }
    for (int a=0; a<=liczba; a++)
    {
        cout << setw(max_length) << TAB[a] << endl;
    }
    cin.get();
    return 0;
}