Re: print all permutations of string

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anurag wrote:


IIRC, this favour has been requested a number of times in recent weeks.
I wonder why the sudden interest in permuting strings using C
functions.

In any case, to give a concrete example of what R.H. discusses
elsethread, here's an attempt I made a few weeks ago, when the question
first came up. Take it as you will.

For the regulars: yes I know that answering a homework question is
frowned apon, and even worse is answering an algorithm question, but
this one piqued my interest. So, for my one freebie a year, I post this
code ;-)

==snip==

#include <stdio.h>
#include <stdlib.h>
#include <string.h>

void rotate(unsigned length, char *string)
{
  char save;

  save = *string;
  while(--length)
  {
    *string=*(string+1);
    ++string;
  }
  *string = save;
}

void permute(unsigned length, char *string, unsigned depth)
{

  if (length == 0)
    printf("%s\n",string-depth);
  else
  {
    unsigned count;

    for (count = length ; count > 0; --count)
    {
      permute(length-1,string+1,depth+1);
      rotate(length,string);
    }
  }

}

int main(int argc, char **argv)
{
  while (--argc)
  {
    char *source = malloc(strlen(*++argv)+1);

    if (source)
    {
      strcpy(source,*argv);
      printf("\nPermuting \"%s\"\n",source);

      permute(strlen(source),source,0);

      free(source);
    }
  }
  return EXIT_SUCCESS;
}

==snip==

- --
Lew Pitcher

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