L-12 MCS 275 Mon 5 Feb 2001

/* L-12 MCS 275 drawing patterns on the screen */

/* for width = 16, we create the following pattern:
 x x   x       x
x x   x       x 
 x x x       x  
x x x       x   
   x x x   x    
  x x x   x     
 x   x x x      
x   x x x       
       x x x   x
      x x x   x 
     x   x x x  
    x   x x x   
   x       x x x
  x       x x x 
 x       x   x x
x       x   x x 
*/

#include <stdio.h>
#define SYMBOL 'x'

void draw (int width);
/* draws a pattern on a grid of size width times width on the screen */
void make_pattern (int width, char grid[width][width],
                   int frame_start, int frame_end);
/* creates a pattern in the array grid, for the frame starting
   at position frame_start and ending at frame_end-1 */

int main()
{
   int width;

   printf("Drawing a pattern on the screen.\n");
   printf("  Give screen width : "); scanf("%d", &width);
   draw(width);
   return 0;
}

void draw (int width)
{
   char pattern[width][width];        /* allocate space for pattern */
   int i,j;

   for (i=0; i < width; i++)            /* initialize the pattern */
      for (j=0; j < width; j++)
         pattern[i][j] = ' ';

   make_pattern(width,pattern,0,width);

   for (i=0; i < width; i++)            /* print the pattern */
   {
      for (j=0; j < width; j++)
         putchar(pattern[i][j]);
      printf("\n");
   }

}

void make_pattern (int width, char grid[width][width],
                   int frame_start, int frame_end)
{
   int i;
   int frame = frame_end-frame_start;

   if (frame > 1)
   {
      for (i=0; i < frame; i++)                   /* mark diagonal on grid */
         grid[frame_start+i][frame_end-1-i] = SYMBOL;
    /* create pattern left of the diagonal */
      make_pattern(width,grid,frame_start,frame_start+frame/2);
    /* create pattern right of the diagonal */
      make_pattern(width,grid,frame_start+frame/2,frame_end);
   }
}