Ubuntu-gr Forum

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

#define NROWS		10
#define NCOLS		10

#define ROW(n)		( (n) / NCOLS )
#define COL(n)		( (n) % NCOLS )

#define POSUP(n)	( (n) - NCOLS )
#define POSDN(n)	( (n) + NCOLS )
#define POSLF(n)	( (n) - 1 )
#define POSRT(n)	( (n) + 1 )

#define MARKS		"BCDEFGHIJKLMNOPQRSTUVWXYZ"

enum Dir { UP=0, DN, LF, RT };


/*********************************************************//**
 *
 ************************************************************/
void tab_print( char tab[] )
{
	for (int n=0; n < NROWS * NCOLS; n++)
	{
		if ( n != 0 && n % NCOLS == 0 )
			putchar('\n');
		putchar( tab[n] );
	}

	putchar('\n');
}

/*********************************************************//**
 *
 ************************************************************/
int next_pos( const int pos, const enum Dir dir)
{
	int ret = -1;

	switch (dir)
	{
		case UP:
			ret = ROW(pos) > 0 ? POSUP(pos) : -1;
			break;
		case DN:
			ret = ROW(pos) < NROWS-1 ? POSDN(pos) : -1;
			break;
		case LF:
			ret = COL(pos) > 0 ? POSLF(pos) : -1;
			break;
		case RT:
			ret = COL(pos) < NCOLS-1 ? POSRT(pos) : -1;
			break;
		default:
			break;
	}

	return ret;
}

/*********************************************************//**
 *
 ************************************************************/
_Bool pos_isblocked( const int pos, const char tab[] )
{
	int nblocked = 0;

	if ( ROW(pos) == 0  || '.' != tab[ POSUP(pos) ] )
		nblocked++;
	if ( ROW(pos) == NROWS-1 || '.' != tab[ POSDN(pos) ] )
		nblocked++;
	if ( COL(pos) == 0 || '.' != tab[ POSLF(pos) ] )
		nblocked++;
	if ( COL(pos) == NCOLS-1 || '.' != tab[ POSRT(pos) ] )
		nblocked++;

printf("%c: nblocked = %d\n", tab[pos], nblocked );
	return 4 == nblocked;
}

/*********************************************************//**
 *
 ************************************************************/
int main( void )
{
	int movesleft, mvcount=0, pos=0;
	char tab[ NROWS * NCOLS ];

	srand( (unsigned)time(NULL) );			/* init pseudo-random seed      */
	memset( tab, '.', sizeof(tab) );		/* init table with dots         */

	tab[0] 		= 'A';
	movesleft 	= strlen(MARKS);
	while ( movesleft )
	{
		int try = 0;

		if ( pos_isblocked(pos, tab) )
			break;
		do {
			try = next_pos( pos, rand() % 4 );
		} while ( -1 == try || '.' != tab[try] );

		pos = try;
		tab[ pos ] = MARKS[ mvcount++ ];
		movesleft--;
	}
	tab_print( tab );

	exit( EXIT_SUCCESS );
}