goscore.c

/*
 * access the array b at row d, column e. Allow extra index parts before the
 * closing bracket. Usually used as I] to get b[d * g + e]. All occurances of
 * this macros are commented in the next parts.
 */
#define I b[d*g+e

/* int */ a;		/* updated content of cell at b[d*g+e] */
/* int */ b[65536];	/* array containing the board */
/* int */ c;		/* cleared if the flood-fill fills something, score */
/* int */ d;		/* variable for the input loop, y coordinate */
/* int */ e;		/* x coordinate */
/* int */ f;		/* number of positions used up in b */
/* int */ g;		/* size of the board, e.g. 19 for a 19x19 board */

/*
 * The board itself contains at each position the bitwise or of the following
 * values:
 *
 *   1 -- intersection coloured white
 *   2 -- intersection coloured black
 *   4 -- intersection occupied
 *
 * With a value of "0" meaning "empty intersection".
 */

/* int */ main()
{
	/* read in the go board. Because EOF == -1, getchar() + 1 is 0 on EOF */
	for(; d = getchar() + 1; f++)
		b[f]
		    = d - 80	/* 'O' + 1 */
		    ? d - 89	/* 'X' + 1 */
		    ? d - 46	/* '-' + 1 */
		    ? f--	/* if no match, undo effect of f++ */
		    : 0		/* if empty, b[f] = 0; */
		    : 5		/* if black, b[f] = 4 + 1; */
		    : 6,	/* if white, b[f] = 4 + 2; */
		g += g * g < f;	/* incrementially compute board size as sqrt(f) */

	/*
	 * Flood-fill algorithm. Iterate as long as c cleared (i.e. something
	 * was filled). !c++ evaluates to 1 if c was 0 (cleared) before and sets
	 * c again.
	 */
	while (!c--)	/* as long as we change parts of the board */
		/* iterate over the board with coordinates (e,d) backwards */
		for (d = g; d--;) for (e = g; e--;)
			I] < 3 ? a	/* if b[d*g+e] is unoccupied, set a to */
				= I]	/* b[d*g+e] */
				| !!d * I - g]	/* if d != 0, b[(d-1)*g + e] */
				| !!e * I - 1]	/* if e != 0, b[d*g + e - 1] */
				| (d < g - 1) * I + g]	/* if d < g - 1, b[(d+1)*g + e] */
				| (e < g - 1) * I + 1],	/* if e < g - 1, b[d*g + e + 1] */
			a &= 3,		/* clear occupied bit */
			c &= I] == a,	/* if value of b[d*g+e] changed, clear c */
			I] = a		/* write back cell content */
			: 0;		/* do nothing otherwise */

	/* count score walking backwards down the array */
	while (f--)
		/* if black, count 1; if white, count -1 */
		c += b[f] % 2 - b[f] / 2 % 2;

	/* print the result, print Jigo if c == 0 */
	printf(c ? "%c+%i" : "Jigo", c > 0 ? 66 : 87, abs(c));
}