Simple Recursion problem

[codyjae]

Ok, so I have this assignment where i have to create a program that takes in input for the length of string and amount of ones and produce an ordered output for the ones and length...

i.e.

UNIX>enum 3 1
001
010
100

or

UNIX>enum 2 1
01
10

where the input is enum (length) (amount of ones)

Well all i can do through recursion is the very first output before it goes away. and when i do fit in more than one line, it seg faults at the second line.. i.e
UNIX>enum 3 1
001
010
Seg Fault()

Can Anyone help me???
here is my code for the class:

class Enum
{
    public:
        Enum(int);
        int do_enumeration(int, int);
        int ones;
    protected:
        string word;
        int lenth;
        int zero;
};

Enum::Enum(int size)
{
    lenth = size;
    word = "";
    for (int i = 0; i < size; i++)
    {
        word+= '0';
    }
    ones = 0;
    zero = 0;

}

int Enum::do_enumeration(int index, int number)
{
    if (index == lenth && zero == (lenth - ones))
    {
        cout << word << endl;
        return 0;
    }
    else
    {
        if(zero < lenth - ones)
        {
            zero++;
            word[index] = '0';
            do_enumeration(index + 1, number);
            //number++;
            //zero--;
        }
        if(number != 0)
        {
            word[index] = '1';
            do_enumeration(index + 1, number - 1);
            number++;
            word[index] = '0';
        }
    }

    return 0;
}

I'm new here so i don't know if this is appropriate or in the proper manner. so i apologize if its incorrect

the commented out code is what i put in to have two lines of output before seg fault

[codyjae]

I got it figured out guys, but that brings on a different question... Why does it work?? and is there a more intelligent way of doing it?

here is my solution:

int Enum::do_enumeration(int index, int number)
{
    if (index == lenth && number == 0)
    {
        cout << word << endl;
        return 0;
    }
    else
    {
        if(zero < lenth - ones)
        {
            zero++;
            word[index] = '0';
            do_enumeration(index + 1, number);
            //number++;
            zero--;
        }
        if(number != 0)
        {
            word[index] = '1';
            do_enumeration(index + 1, number - 1);
            number++;
            word[index] = '0';
        }
    }

    return 0;
}

Thanks ahead of time