/* demo.src/qsort.c; cpl4.10 */

void swap(short* line_num, int i, int j);
char Switch(void* v[], short first, short second, short* line_num);
void qqsort(void* v[], short* line_num, int left, int right);


/* qqsort: sort v[left],...,v[right] into increasing order */
void qqsort(void* v[], short* line_num, int left, int right)
{
    int i, last;
    if (left >= right)
        return;
    swap(line_num, left, (left + right)/2);  /* move partition element */
    last = left;
    for (i = left+1; i <= right; i++) {/* partition */
        if (Switch(v,i,left,line_num))
            {swap(line_num, ++last, i);}
	}

    swap(line_num, left, last);    /* restore partition element */
    qqsort(v, line_num, left, last-1);
    qqsort(v, line_num, last+1, right);
}

char Switch(void* v[], short first, short second, short* line_num){
/* return true 0 if first and second need to be switched
otherwise return non-zero  
If the first line is contained in the second we don't switch -
if the second line is contained in the first we do. 
*/
	char	*ff, *tt;


ff=(char*)v[line_num[first]];
tt=(char*)v[line_num[second]];
for(; *ff!=0 && *tt!=0; ff++, tt++) {
  if( (*ff)<(*tt) ) return 1;
  else if( (*ff) > (*tt) ) return 0;
  }
if( *ff==0 ) return 1; else return 0;
	
}

/* swap: interchange v[i] and v[j] */
void swap(short* v, int i, int j)
{
    short temp;

    temp = v[i];
    v[i] = v[j];
    v[j] = temp;
}