Coder Radio Challenge #1

main.c

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

#define LEN(x) (sizeof(x) / sizeof(x[0]))

#define NUM_USER_HANDS   (28)
#define NUM_DEALER_HANDS (10)
#define CHART_SIZE       (NUM_USER_HANDS * NUM_DEALER_HANDS)

#define	H  (1) /* Hit */
#define S  (2) /* Stand */
#define D  (3) /* Double if allowed, otherwise Hit */
#define DS (4) /* Double if allowed, otherwise Stand */
#define SP (5) /* Split */
#define XH (6) /* Surrender if allowed, otherwise Hit */
#define XP (7) /* Surrender if allowed, otherwise Split */
#define XS (8) /* Surrender if allowed, otherwise Stand */

/* Help */
static const char *HELP =
"usage: %s [USER HAND] [DEALER HAND]\n"
"for example: %s A,5 7\n"
"\n";

/* User hands */
static char *user_hands[NUM_USER_HANDS] = {
	"8",
	"9",
	"10",
	"11",
	"12",
	"13",
	"14",
	"15",
	"16",
	"17",
	"A,2",
	"A,3",
	"A,4",
	"A,5",
	"A,6",
	"A,7",
	"A,8",
	"A,9",
	"2,2",
	"3,3",
	"4,4",
	"5,5",
	"6,6",
	"7,7",
	"8,8",
	"9,9",
	"10,10",
	"A,A"
};

/* Dealer hands */
static char *dealer_hands[NUM_DEALER_HANDS] = {
	"2",
	"3",
	"4",
	"5",
	"6",
	"7",
	"8",
	"9",
	"10",
	"A",
};

/* Strategy chart */
static char chart[CHART_SIZE] = {
/*           2   3   4   5   6   7   8   9  10   A */
/*     8 */  H,  H,  H,  H,  H,  H,  H,  H,  H,  H,
/*     9 */  H,  D,  D,  D,  D,  H,  H,  H,  H,  H,
/*    10 */  D,  D,  D,  D,  D,  D,  D,  D,  H,  H,
/*    11 */  D,  D,  D,  D,  D,  D,  D,  D,  D,  D,
/*    12 */  H,  H,  S,  S,  S,  H,  H,  H,  H,  H,
/*    13 */  S,  S,  S,  S,  S,  H,  H,  H,  H,  H,
/*    14 */  S,  S,  S,  S,  S,  H,  H,  H,  H,  H,
/*    15 */  S,  S,  S,  S,  S,  H,  H,  H, XH, XH,
/*    16 */  S,  S,  S,  S,  S,  H,  H, XH, XH, XH,
/*    17 */  S,  S,  S,  S,  S,  S,  S,  S,  S, XS,
/*   A,2 */  H,  H,  H,  D,  D,  H,  H,  H,  H,  H,
/*   A,3 */  H,  H,  H,  D,  D,  H,  H,  H,  H,  H,
/*   A,4 */  H,  H,  D,  D,  D,  H,  H,  H,  H,  H,
/*   A,5 */  H,  H,  D,  D,  D,  H,  H,  H,  H,  H,
/*   A,6 */  H,  D,  D,  D,  D,  H,  H,  H,  H,  H,
/*   A,7 */  S, DS, DS, DS, DS,  S,  S,  H,  H,  H,
/*   A,8 */  S,  S,  S,  S,  S,  S,  S,  S,  S,  S,
/*   A,9 */  S,  S,  S,  S,  S,  S,  S,  S,  S,  S,
/*   2,2 */ SP, SP, SP, SP, SP, SP,  H,  H,  H,  H,
/*   3,3 */ SP, SP, SP, SP, SP, SP,  H,  H,  H,  H,
/*   4,4 */  H,  H,  H, SP, SP,  H,  H,  H,  H,  H,
/*   5,5 */  D,  D,  D,  D,  D,  D,  D,  D,  H,  H,
/*   6,6 */ SP, SP, SP, SP, SP,  H,  H,  H,  H,  H,
/*   7,7 */ SP, SP, SP, SP, SP, SP,  H,  H,  H,  H,
/*   8,8 */ SP, SP, SP, SP, SP, SP, SP, SP, SP, XP,
/*   9,9 */ SP, SP, SP, SP, SP,  S, SP, SP,  S,  S,
/* 10,10 */  S,  S,  S,  S,  S,  S,  S,  S,  S,  S,
/*   A,A */ SP, SP, SP, SP, SP, SP, SP, SP, SP, SP,
};

static int find_user_hand(const char *s)
{
	int i;

	for (i = 0; i < LEN(user_hands); i++) {
		if (strcmp(s, user_hands[i]) == 0)
			return i;
	}

	return -1;
}

static int find_dealer_hand(const char *s)
{
	int i;

	for (i = 0; i < LEN(dealer_hands); i++) {
		if (strcmp(s, dealer_hands[i]) == 0)
			return i;
	}

	return -1;
}

static const char * suggest_action(int user_hand_index, int dealer_hand_index)
{
	const char *s;
	int chart_index;
	int action_code;

	/* Check user hand index */
	if (user_hand_index < 0 || user_hand_index > NUM_USER_HANDS) {
		fprintf(stdout, "invalid user hand index: %d\n", user_hand_index);
		return NULL;
	}

	/* Check dealer hand index */
	if (dealer_hand_index < 0 || dealer_hand_index > NUM_USER_HANDS) {
		fprintf(stdout, "invalid dealer hand index: %d\n", dealer_hand_index);
		return NULL;
	}

	/* Determine action code from the chart */
	chart_index = dealer_hand_index + user_hand_index * LEN(dealer_hands);
	action_code = chart[chart_index];

	/* Convert action code into human-readable string */
	switch (action_code) {
	case H:
		s = "Hit";
		break;

	case S:
		s = "Stand";
		break;

	case D:
		s = "Double if allowed, otherwise Hit";
		break;

	case DS:
		s = "Double if allowed, otherwise Stand";
		break;

	case SP:
		s = "Split";
		break;

	case XH:
		s = "Surrender if allowed, otherwise Hit";
		break;

	case XP:
		s = "Surrender if allowed, otherwise Split";
		break;

	case XS:
		s = "Surrender if allowed, otherwise Stand";
		break;

	default:
		s = "(unknown action)";
	}

	return s;
}

int main(int argc, char **argv)
{
	int user_hand_index;
	int dealer_hand_index;

	/* Print help */
	if (argc < 3) {
		fprintf(stdout, HELP, argv[0], argv[0]);
		return 0;
	}

	/* Find user hand */
	user_hand_index = find_user_hand(argv[1]);
	if (user_hand_index < 0) {
		fprintf(stdout, "invalid user hand\n");
		return -1;
	}
	fprintf(stdout, "user hand:   %s\n", user_hands[user_hand_index]);

	/* Find dealer hand */
	dealer_hand_index = find_dealer_hand(argv[2]);
	if (dealer_hand_index < 0) {
		fprintf(stdout, "invalid dealer hand\n");
		return -1;
	}
	fprintf(stdout, "dealer hand: %s\n", dealer_hands[dealer_hand_index]);

	/* Print suggested action */
	fprintf(stdout, "Suggested action is %s\n", suggest_action(user_hand_index, dealer_hand_index));

	return 0;
}