Advertisement
Not a member of Pastebin yet?
Sign Up,
it unlocks many cool features!
- //Tic-tac-toe playing AI. Exhaustive tree-search. Do what you want with the code.
- //Matthew Steel 2009, www.www.repsilat.com
- #include <stdio.h>
- char gridChar(int i) {
- switch(i) {
- case -1:
- return 'X';
- case 0:
- return ' ';
- case 1:
- return 'O';
- }
- }
- void draw(int b[9]) {
- printf(" %c | %c | %c\n",gridChar(b[0]),gridChar(b[1]),gridChar(b[2]));
- printf("---+---+---\n");
- printf(" %c | %c | %c\n",gridChar(b[3]),gridChar(b[4]),gridChar(b[5]));
- printf("---+---+---\n");
- printf(" %c | %c | %c\n",gridChar(b[6]),gridChar(b[7]),gridChar(b[8]));
- }
- int win(const int board[9]) {
- //determines if a player has won, returns 0 otherwise.
- unsigned wins[8][3] = {{0,1,2},{3,4,5},{6,7,8},{0,3,6},{1,4,7},{2,5,8},{0,4,8},{2,4,6}};
- int i;
- for(i = 0; i < 8; ++i) {
- if(board[wins[i][0]] != 0 &&
- board[wins[i][0]] == board[wins[i][1]] &&
- board[wins[i][0]] == board[wins[i][2]])
- return board[wins[i][2]];
- }
- return 0;
- }
- int minimax(int board[9], int player) {
- //How is the position like for player (their turn) on board?
- int winner = win(board);
- if(winner != 0) return winner*player;
- int move = -1;
- int score = -2;//Losing moves are preferred to no move
- int i;
- for(i = 0; i < 9; ++i) {//For all moves,
- if(board[i] == 0) {//If legal,
- board[i] = player;//Try the move
- int thisScore = -minimax(board, player*-1);
- if(thisScore > score) {
- score = thisScore;
- move = i;
- }//Pick the one that's worst for the opponent
- board[i] = 0;//Reset board after try
- }
- }
- if(move == -1) return 0;
- return score;
- }
- void computerMove(int board[9]) {
- int move = -1;
- int score = -2;
- int i;
- for(i = 0; i < 9; ++i) {
- if(board[i] == 0) {
- board[i] = 1;
- int tempScore = -minimax(board, -1);
- board[i] = 0;
- if(tempScore > score) {
- score = tempScore;
- move = i;
- }
- }
- }
- //returns a score based on minimax tree at a given node.
- board[move] = 1;
- }
- void playerMove(int board[9]) {
- int move = 0;
- do {
- printf("\nInput move ([0..8]): ");
- scanf("%d", &move);
- printf("\n");
- } while (move >= 9 || move < 0 && board[move] == 0);
- board[move] = -1;
- }
- int main() {
- int board[9] = {0,0,0,0,0,0,0,0,0};
- //computer squares are 1, player squares are -1.
- printf("Computer: O, You: X\nPlay (1)st or (2)nd? ");
- int player=0;
- scanf("%d",&player);
- printf("\n");
- unsigned turn;
- for(turn = 0; turn < 9 && win(board) == 0; ++turn) {
- if((turn+player) % 2 == 0)
- computerMove(board);
- else {
- draw(board);
- playerMove(board);
- }
- }
- switch(win(board)) {
- case 0:
- printf("A draw. Ho hum.\n");
- break;
- case 1:
- draw(board);
- printf("You lose.\n");
- break;
- case -1:
- printf("You win. Inconceivable!\n");
- break;
- }
- }
Advertisement
Add Comment
Please, Sign In to add comment
Advertisement