ttt.h

#ifndef _TTT_H
#include <stdlib.h>
#include <stdio.h>
#include <string.h>
#define _TTT_H

#define HSIZE   19683   // 3^9
#define BSIZE   31      // 6 characters per line, 5 lines, and \0

// represents a board
typedef char Board[BSIZE];

// start board string declared in ttt.c
extern Board START_BOARD;

// external array that maps the playable positions to their indices in the 
// board string
extern int pos2idx[9];

// external array of row, column and diagonal positions

extern int WINS[8][3];

// board nodes for graph
struct BoardNode
{
  char init;            // 0=not initialized, or 1=initialized
  char turn;            // 'X', 'O', '-'=board is full (game over)
  int depth;            // depth of the node in the graph = moves played
  Board board;          // printable board file
  char winner;          // 'X', 'O', '-' (tie), '?' (game in progress)
  int move[9];          // board hashes for all move positions; -1=illegal move
  int score;		// winner of the game if both players play smartly
                        // 1=X -1=O 0=tie
};

// htable declared in ttt.c
extern struct BoardNode htable[HSIZE];

int board_hash( Board board );
int imax( int a, int b );
int imin( int a, int b );
void init_boards();
char winner( Board board );
int depth( Board board );
char turn( Board board );
void init_board( Board board );
void join_graph( Board board );
void compute_score();
int best_move( int board );
void print_node( struct BoardNode board_node );
#endif