How to generate all possible variations with repetitions in C

Question

I'm looking for an algorithm in C to generate all possible variations with repetitions for set length and from n elements. For example, if the length is 3 and the elements are: 1, 2. The output should be :

1 1 1

1 1 0

1 0 0

1 0 1

0 0 0

0 0 1

0 1 1

0 1 0

I already looked for the solutions here, but all I could find were implementations in Java or Python and I don't know how to rewrite them to C. Can somebody please post a C code for this problem here?

"I don't know how to rewrite them to C" I assume the purpose of your assignment is to learn to write enough C to do the job. What have you tried? If you don't know enough to write this, what will you do with the code you receive? Represent it as your own? — The Archetypal Paul, Dec 02 '10 at 17:21
"Can somebody please post a C code for this problem here?" No; the reason you're being asked to do this is so that you actually learn something. — Karl Knechtel, Dec 02 '10 at 17:29

score 4 · Answer 1 · edited Jan 16 '19 at 08:45

4

void g(int l,int v,char *c)
{
    int i=v;
    if (l--==0) 
        puts(c);
    else 
        while(i)
            g(l,(c[l]='0'+--i,v),c);
}

void f(int l,int v)
{
    char c[l+2];
    g(((c[l]=13,c[l+1]=0),l),v,c);
}

int main()
{
    f(3,2);
    return 0;
}

Tested, works!, updated to fix readability issue

edited Jan 16 '19 at 08:45

Darius Kucinskas

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answered Dec 02 '10 at 17:38

The Archetypal Paul

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And it better work, it's easier to write a new one than to debug **THIS** :) – ruslik Dec 02 '10 at 17:45
I could see somebody being dropped off the subject, oh dear. – Andreas Wong Dec 02 '10 at 17:54
By the way, last I checked, over 10 years ago that is, `char c[l+2];` was not standard C. Unless the standard has changed, this just something gcc lets you get away with. – Dima Dec 03 '10 at 15:59
Dima, you've removed the entire pont of my post. If you're going to do that, finish the job and rename the variables, remove the comma-expressions etc. I'm rolling back your change. – The Archetypal Paul Dec 03 '10 at 16:01
And it is allowed in C99 - http://stackoverflow.com/questions/448844/variable-sized-arrays-in-c – The Archetypal Paul Dec 03 '10 at 16:03

score 2 · Answer 2 · answered Dec 02 '10 at 17:21

2

It's nothing else than generating all the numbers of length N in base B (in your case N is 3 and B is 2).

answered Dec 02 '10 at 17:21

ruslik

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How to generate all possible variations with repetitions in C

2 Answers2