gistfile1.h

// Simple Mastermind Game
// Copyright (c) Alistair Lynn <arplynn@gmail.com>, 2008

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

// a single playing piece
typedef char MM_Piece;

// PRNG
static const int MM_PRNG_COEFFICIENT = 1103515245;
static const int MM_PRNG_CONSTANT = 12345;
static const int MM_PRNG_SHIFT = 0;
static const int MM_PRNG_MASK = 0x5FFFFFFF;

int MM_Random ( int* seed )
{
	int firstSeed = *seed, output;
	firstSeed *= MM_PRNG_COEFFICIENT;
	firstSeed += MM_PRNG_CONSTANT;
	output = firstSeed >> MM_PRNG_SHIFT;
	output &= MM_PRNG_MASK;
	*seed = firstSeed;
	return output;
}

// a single board
typedef struct _MM_Board
{
	MM_Piece pieces[4];
} MM_Board;

// a record of a game
typedef struct _MM_Game
{
	int nGames, seed;
	MM_Board target;
	MM_Piece maxPiece;
} MM_Game;

// checks if a piece is valid
bool MM_Piece_IsValid ( MM_Game* game, MM_Piece piece )
{
	return piece >= 'A' &&
	       piece <= game->maxPiece;
}

// generates a random piece
MM_Piece MM_Piece_Random ( MM_Game* game )
{
	return (MM_Random(&(game->seed)) % (game->maxPiece - 'A' + 1)) + 'A';
}

// compares two boards, giving numbers of matches and misplacements
void MM_Board_Compare ( MM_Board board1, MM_Board board2, int* matches, int* misplacements )
{
	int i, j, nmatches = 0, nmisplacements = 0, usedMatches = 0;
	for (i = 0; i < 4; i++)
	{
		if (board1.pieces[i] == board2.pieces[i])
		{
			usedMatches |= (1 << i);
			nmatches++;
		}
	}
	for (i = 0; i < 4; i++)
	{
		for (j = 0; j < 4; j++)
		{
			if (j == i) continue;
			if (!(usedMatches & (1 << j)) && (board1.pieces[i] == board2.pieces[j]))
			{
				usedMatches |= (1 << j);
				nmisplacements++;
			}
		}
	}
	*matches = nmatches;
	*misplacements = nmisplacements;
}

// sets up a game
void MM_InitGame ( MM_Game* game, MM_Piece maxPiece, int seed, int nGames )
{
	game->nGames = nGames;
	game->seed = seed;
	game->maxPiece = maxPiece;
	game->target.pieces[0] = MM_Piece_Random(game);
	game->target.pieces[1] = MM_Piece_Random(game);
	game->target.pieces[2] = MM_Piece_Random(game);
	game->target.pieces[3] = MM_Piece_Random(game);
}

// do a single turn, interacting with the user
void MM_TakeTurn ( MM_Game* game )
{
	size_t len;
	char inBuffer[6];
	int matches, misplacements, i;
	MM_Board inBoard;
	if (fgets(inBuffer, sizeof(inBuffer), stdin) == &(inBuffer[0]))
	{
		len = strlen(inBuffer);
		if (len != 4 && len != 5)
		{
			printf("\twrong number of characters\n");
			return;
		}
		else if (len == 5)
		{
			inBuffer[4] = 0; // strip newline
		}
		// check piece validity
		for (i = 0; i < 4; i++)
		{
			if (!MM_Piece_IsValid(game, inBuffer[i]))
			{
				printf("\tbad piece: %c\n", inBuffer[i]);
				return;
			}
			inBoard.pieces[i] = inBuffer[i];
		}
		MM_Board_Compare(inBoard, game->target, &matches, &misplacements);
		if (matches == 4)
		{
			printf("\tSolved.\n");
			exit(0);
		}
		else
		{
			printf("\tMatches: %d\n\tMisplacements: %d\n", matches, misplacements);
			game->nGames--;
			if (game->nGames == 0)
			{
				printf("\tGame over. The board was:\n\t");
				fwrite(&(game->target), sizeof(MM_Board), 1, stdout);
				putchar('\n');
				exit(0);
			}
		}
	}
	else
	{
		printf("\tfgets() failed, try again.\n");
	}
}

int main ( int argc, char** argv )
{
	MM_Game game;
	MM_Piece maxPiece;
	int seed, nGames;
	if (argc != 4)
	{
		printf("Usage: %s [max] [seed] [turns]\n", argv[0]);
		return 1;
	}
	maxPiece = *argv[1];
	seed = atoi(argv[2]);
	nGames = atoi(argv[3]);
	MM_InitGame(&game, maxPiece, seed, nGames);
	printf("Mastermind, v1.0.0\n");
	printf("Copyright (c) Alistair Lynn <arplynn@gmail.com> 2009\n");
	while (1)
	{
		MM_TakeTurn(&game);
	}
	// make the compiler happy
	return 0;
}