------------------------------------------------- permut.c -----------------------
#include <stdio.h>
#include <stdlib.h>

static int num = 2;
static int index = 0;
static int old = 0;
static int minfree = 0;
static int *f = NULL;
static int *c = NULL;

void freespot(const int ind)
{
   if(ind >= 0){
      f[ind] = 1;
      if(ind < minfree){
         minfree = ind;
      }
   }
}
void takespot(const int ind)
{
   if(ind >= 0){
      f[ind] = 0;
      if(ind == minfree){
         int i = 0;
         for(i = minfree+1; i < num; ++i){
            if(f[i] == 1){
               minfree = i;
               break;
            }
         }
      }
   }
}
void perm()
{
   int count = 1;
   while(index >= 0){
      int start = c[index]+1;
      if(start == 0){
         start = minfree;
      }
      int i = start;
      for(i; i < num; ++i){
         if(f[i] == 1){
            freespot(c[index]);
            takespot(i);
            c[index] = i;
            if(index < num-1){
               index++;
            }else{
               freespot(i);
               int j = 0;
               if(num > 100){
                  for(j = 0; j < 10; ++j){
                     fprintf(stdout, "%i ", c[j]);
                  }
                  fprintf(stdout, "... ");
                  for(j = num-10; j < num; ++j){
                     fprintf(stdout, "%i ", c[j]);
                  }
               }else{
                  for(j = 0; j < num; ++j){
                     fprintf(stdout, "%i ", c[j]);
                  }
               }
               fprintf(stdout, "| %i\n", count);
               count++;
            }
            break;
         }
      }
      if(index == old){
         freespot(c[index]);
         c[index] = -1;
         index--;
      }
      old = index;
   } 
}

int main(int argc, char **argv)
{

   if(argc > 1){
      num = atoi(argv[1]);
      if(num < 2){
         num = 2;
      }
   }
   f = malloc(num*sizeof(int));
   c = malloc(num*sizeof(int));
   int i = 0;
   for(i = 0; i < num; ++i){
      c[i] = -1;
      f[i] = 1;
   }
   fprintf(stdout, "Init fertig %i\n", num);
   perm();
   return 0;
}