recursive algorithm

i'm having a problem with below recursive code.
there are 4 chars stored in a array, 'a', 'b', 'c', 'd'. input is between 1 and 16, and output should look like this:

when input is 1:
a
b
c
d

when iput is 2:
aa
ab
ac
ad
ba
bb
bc
bd
ca
cb
cc
cd
da
db
dc
dd

and so on...

here is the code i'v been working:

Code:

void f(int x, int num)
{
	int i;
        char a[4] = {'a', 'b', 'c', 'd'};
	char temp[16];

	if(num == 0)
		return;

	else
		for(i = 0; i < 4; i++)
		{
			temp[x] = a[i];

			f(x + 1, num - 1);

			temp[x + 1] = '\0';

			printf("%s\n", temp);
		}
}

where should i change to make it work?

What isn't working now? You need to be more specific about that so we know where to look.

Originally Posted by sean_mackrory

What isn't working now? You need to be more specific about that so we know where to look.

ok...
when u run the above code, u get this result:

Code:

$ ./test.out
Enter a number between 1 and 16: 1
a
b
c
d

$ ./test.out
Enter a number between 1 and 16: 2
 a
 b
 c
 d
a
 a
 b
 c
 d
b
 a
 b
 c
 d
c
 a
 b
 c
 d
d

here is the full code:

Code:

#include <stdio.h>
 
void f(int, int, int);
 
int main(void)
{
        int x = 0, num;
 
        printf("Enter a number between 1 and 16: ");
        scanf("%d", &num);
 
        if (num < 1 || num > 16)
                printf("-> %d is not a valid number.\n", num);
 
        else
                f(x, num, num);
}
 
void f(int x, int n, int num)
{
        int i;
        char a[4] = {'a', 'b', 'c', 'd'};
        char temp[16];
 
        if(num == 0)
                return;
 
        else
                for(i = 0; i < 4; i++)
                {
                        temp[x] = a[i];
 
                        f(x + 1, n, num - 1);     // here?
 
                        temp[x + 1] = '\0';
 
                        printf("%s\n", temp);     // and maybe here?
                }
}

I like these types of problems. Always good for a little dusting of the skills
Here is my solution done up as much like yours as possible. Things I would notice: When I do the print, how I declared the array (note you don't have to do yours dynamically I did just for kicks)

Code:

#include <stdio.h>
#include <stdlib.h>
void f(const int num, const int pos)
{
  static const char a[4] = {'a', 'b', 'c', 'd'};
  static char *array;
  int counter;
  if ( pos == 0 )
    array = malloc (num + 1);

  if ( pos >= num )
  {
    array[num] = '\0';
    puts(array);
    return;
  }

  for (counter=0; counter<sizeof a; counter++)
  {
    array[pos]=a[counter];
    f(num, pos+1);
  }

  if ( pos == 0)
    free(array);

}

int main(void) {
  f(3,0);
  putchar('\n');
  return 0;
}

thanks alot, Thantos.