Snake game boundary checking - c++

I am writing a simple console snake game,when the 'O' snake hits the wall '#' it's game over but for some reason it ends one before the wall from left to right,top and bottom works fine.
I tried debugging by printing y(I know should be the other way around not good design by me) and y displays it's position as 0 just before the wall so does that mean the wall is -1? but it can't possibly be -1 because I set i = 0 not -1,
so flustered as to whats going wrong also note my code is quite messy but I am pretty new and still learning good style
void draw(){
system("cls");
bool notFirst = false;
bool notLast = false;
for(int i = 0; i <= HEIGHT+2; i++){
for(int j = 0; j <= WIDTH+2; j++){
if(i > 0){
notFirst = false;
}
if(i < HEIGHT+2){
notLast = false;
}
if(i == 0 && j <= WIDTH-1){
cout << "#"; // top wall
notFirst = true;
}
if(i == HEIGHT+2 && j <= WIDTH-2){
cout << "#"; // bottom wall
notLast = true;
}
if(j == 0 && i != 0){
cout << "#"; // #
}
if(j == WIDTH-1){
cout << "#";
}
if(x == i && y == j){
if(x == 0 || x == HEIGHT+2){
gameOver = true;
}
if(y == 0){
gameOver = true;
}
cout << y; // DEBUG
cout << "O";
}
else if(fruitX == i && fruitY == j){
cout << "F";
}
else{
if(!notFirst && !notLast){
cout << " ";
}
}
}
cout << endl;
}
}
int main()
{
setUp();
while(!gameOver){
draw();
input();
logic();
}
}

Related

C++ Tic tac toe minimax

I am trying to create a c++ unbeatable tic tac toe AI. after watching several videos on the topic i thought I had it all figured out. An error pops up on the screen saying "Expression: vector subscript out of range". I believe the error is coming from the availableMoves() function. however I do not know why.
The game itself works fine. any help would be appreciated.
#include <iostream>
#include <vector>
#include <ctime>
bool in(std::vector<int> v, int element)
{
for (int i = 0; i < v.size(); i++)
{
if (element == v[i])
{
return true;
}
}
return false;
}
class Board
{
private:
char board[3][3] = { {'1', '2', '3'}, {'4', '5', '6'}, {'7', '8', '9'} };
public:
void displayBoard()
{
std::cout << "___________________" << std::endl;
for (int i = 0; i < 3; i++)
{
std::cout << "| ";
for (int j = 0; j < 3; j++)
{
std::cout << board[i][j] << " | ";
}
std::cout << std::endl;
}
std::cout << "___________________" << std::endl;
}
std::vector<int> availableMoves()
{
std::vector<int> moves;
for (int i = 0; i < 3; i++)
{
for (int j = 0; j < 3; j++)
{
if (board[i][j] != 'X' && board[i][j] != 'O')
{
moves.push_back(i * 3 + j);
}
}
}
return moves;
}
void move(int choice, char mark)
{
int y = choice / 3;
int x = choice - y * 3;
board[y][x] = mark;
}
void revert(int choice)
{
int y = choice / 3;
int x = choice - y * 3;
board[y][x] = (char)choice + 48;
}
int checkWin()
{
for (int i = 0; i < 3; i++)
{
if (board[i][0] == board[i][1] && board[i][1] == board[i][2])
{
if (board[i][0] == 'X')
{
return 1;
}
else if (board[i][0] == 'O')
{
return -1;
}
}
}
for (int i = 0; i < 3; i++)
{
if (board[0][i] == board[1][i] && board[1][i] == board[2][i])
{
if (board[0][i] == 'X')
{
return 1;
}
else if (board[0][i] == 'O')
{
return -1;
}
}
}
if (board[0][0] == board[1][1] && board[1][1] == board[2][2])
{
if (board[0][0] == 'X')
{
return 1;
}
else if (board[0][0] == 'O')
{
return -1;
}
}
if (board[0][2] == board[1][1] && board[1][1] == board[2][0])
{
if (board[0][2] == 'X')
{
return 1;
}
else if (board[0][2] == 'O')
{
return -1;
}
}
return 0;
}
int evaluate()
{
return (checkWin() * -1) * (availableMoves().size() + 1);
}
Board& operator=(Board& b)
{
for (int i = 0; i < 3; i++)
{
for (int j = 0; j < 3; j++)
{
board[i][j] = b.board[i][j];
}
}
return (*this);
}
};
class TicTacToe
{
private:
Board board;
int turn;
int searches = 0;
public:
TicTacToe()
{
std::srand(time(0));
turn = std::rand() % 2;
}
int minimax(int depth, Board curBoard, bool is_max)
{
searches++;
if (depth == 0 || curBoard.checkWin() != 0)
{
return board.evaluate();
}
if (is_max)
{
int max_eval = -2147483647;
for (int i = 0; i < curBoard.availableMoves().size(); i++)
{
curBoard.move(curBoard.availableMoves()[i], 'O');
depth -= 1;
int eval = minimax(depth, curBoard, false);
curBoard.revert(curBoard.availableMoves()[i]);
if (eval > max_eval)
{
max_eval = eval;
}
}
return max_eval;
}
if (!is_max)
{
int min_eval = 2147483647;
for (int i = 0; i < curBoard.availableMoves().size(); i++)
{
curBoard.move(curBoard.availableMoves()[i], 'X');
depth -= 1;
int eval = minimax(depth, curBoard, true);
curBoard.revert(curBoard.availableMoves()[i]);
if (eval < min_eval)
{
min_eval = eval;
}
}
return min_eval;
}
}
void game()
{
while (board.checkWin() == 0 && board.availableMoves().size() != 0)
{
board.displayBoard();
if (turn % 2 == 0)
{
std::cout << std::endl;
int choice;
std::cout << "Enter Your Move: ";
std::cin >> choice;
choice -= 1;
while (!in(board.availableMoves(), choice))
{
std::cout << "Enter A Valid Move: ";
std::cin >> choice;
}
board.move(choice, 'X');
std::cout << std::endl;
turn++;
}
board.displayBoard();
if (board.checkWin() != 0)
{
break;
}
if (turn % 2 == 1)
{
int ai = minimax(9 - (turn % 2), board, true);
std::cout << searches;
std::cin.get();
turn++;
}
}
if (board.checkWin() == 1)
{
std::cout << "You Won" << std::endl;
}
else if (board.checkWin() == -1)
{
std::cout << "You Lost" << std::endl;
}
else
{
std::cout << "Tie" << std::endl;
}
std::cout << "Would You Like To Play Again Y/N: ";
char playAgain;
std::cin >> playAgain;
if (playAgain == 'Y')
{
Board newBoard;
board = newBoard;
game();
}
}
};
int main()
{
TicTacToe ticTacToe;
ticTacToe.game();
}
Do you know how to debug? If not, you should definitely learn this, it's pretty helpful. But here's some things I found out.
The problem is not in availableMoves(), but in minimax(), more precisely in line 215, where the program calls curBoard. revert(curBoard. availableMoves()[i]).
void revert(int choice)
{
int y = choice / 3;
int x = choice - y * 3;
board[y][x] = (char)choice + 48;
}
for (int i = 0; i < curBoard.availableMoves().size(); i++)
{
curBoard.move(curBoard.availableMoves()[i], 'X');
depth -= 1;
int eval = minimax(depth, curBoard, true);
curBoard.revert(curBoard.availableMoves()[i]);
if (eval < min_eval)
{
min_eval = eval;
}
}
The error happens in the function revert, but I am not sure why. Maybe availableMoves also returns something wrong. Variable i is permanently 0 in the for-loop. So it is possible that there is something wrong at position 0 of the vector moves, which revert cannot handle. Try debugging yourself, maybe you'll find the problem.

Computer Player for a Gomoku Game in C++ [closed]

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A few time ago I made a game similar to Gomoku in C++ that is taking between two players.
Now I want to make it Player vs Computer.
I tried to do it in simplest way, by making a function of computer to pick a random cell but I still haven't succeeded.
I understood that in order of getting a random number I can use rand() and for a letter something like this:
char letters[] = "abcdefghijklmnopqrstuvwxyz";
char x = letters[rand() % 26];
Can someone help me and describe how to implement a computer player?
This is my implementation so far:
#include <iostream>
#include <iomanip>
using namespace std;
void print_table(int x[][15]) {
system("cls");
for (int i = 0; i < 15; i++) {//the loop that use to print out the english character row
if (i == 0)
cout << setw(4) << "A";
else if (i == 1)
cout << " B";
else if (i == 2)
cout << " C";
else if (i == 3)
cout << " D";
else if (i == 4)
cout << " E";
else if (i == 5)
cout << " F";
else if (i == 6)
cout << " G";
else if (i == 7)
cout << " H";
else if (i == 8)
cout << " I";
else if (i == 9)
cout << " J";
else if (i == 10)
cout << " K";
else if (i == 11)
cout << " L";
else if (i == 12)
cout << " M";
else if (i == 13)
cout << " N";
else if (i == 14)
cout << " O";
else if (i == 15)
cout << " P";
}
cout << endl;
for (int i = 0; i < 15; i++) {
cout << setw(2) << i;//print out the row number
for (int j = 0; j < 15; j++) {//print out the board game.
if (x[i][j] == 0) {//the inital value is 0, so when the block is 0 then print out the '.'
cout << " .";
}
else if (x[i][j] == 1) {//when the player O input the block then the value will adding one then if check the block is one then output the 'o'
cout << " O";
}
else if (x[i][j] == 2) {//when the player X input the block then the value will adding two then if check the block is two then output the 'x'
cout << " X";
}
}
cout << endl;
}
}
int check_player(int p) {
if (p == 1) {//change the player everytime before the next loop compile
p++;
}
else {
p--;
}
return p;
}
void input_value(int &t, int &n, int p, int x[][15]) {
char eng;
int number;
do {//the loop that ask for the user input the location.
cout << "player ";
if (p == 1) {
cout << "O";
}
else {
cout << "X";
}
cout << ", make a move: ";
cin >> eng;//input the location
cin >> number;
if (eng == 'A')//change the character to different number
t = 0;
else if (eng == 'B')
t = 1;
else if (eng == 'C')
t = 2;
else if (eng == 'D')
t = 3;
else if (eng == 'E')
t = 4;
else if (eng == 'F')
t = 5;
else if (eng == 'G')
t = 6;
else if (eng == 'H')
t = 7;
else if (eng == 'I')
t = 8;
else if (eng == 'J')
t = 9;
else if (eng == 'K')
t = 10;
else if (eng == 'L')
t = 11;
else if (eng == 'M')
t = 12;
else if (eng == 'N')
t = 13;
else if (eng == 'O')
t = 14;
if (!(eng >= 'A'&&eng <= 'M') || !(number >= 0 && number <= 14) || x[number][t] != 0) {//when the input wrong, output the statement to ask anouther input and loop again.
cout << "Invaid input, Try again!" << endl;
continue;
}
else {//if no problem then this input loop is break and jump to the next statement
break;
}
} while (1);//Because it will break as well so the do-while loop is no any requirement
n = number;
}
int main() {
const int num = 15;//the number for constant the array row and column value
char check_e;//for the user input the column
int R[num][num] = { 0 }, check_n, player = 1, buger = 0, transfer, playerO_win = 0, playerX_win = 0, draw = 0, check_draw;//the variable that for user input or checking the game statment
do {//launch the loop for the user input again and again
check_draw = 0;//reset the checking of draw
print_table(R);
input_value(transfer, check_n, player, R);
R[check_n][transfer] += player;//change the value according the player's input and the player name.
for (int i = 0; i < num; i++) {
for (int j = 0; j < num; j++) {
if (i <= 8 && R[j][i] != 0 && (R[j][i] == R[j][i + 1] && R[j][i] == R[j][i + +2] && R[j][i] == R[j][i + 3] && R[j][i] == R[j][i + 4])) {//the checking for the row bingo
if (R[j][i] == 1) {
playerO_win++;
break;
}
else {
playerX_win++;
break;
}
}
else if (j <= 8 && R[j][i] != 0 && (R[j][i] == R[j + 1][i] && R[j][i] == R[j + 2][i] && R[j][i] == R[j + 3][i] && R[j][i] == R[j + 4][i])) {//the checking for the column bingo
if (R[j][i] == 1) {
playerO_win++;
break;
}
else {
playerX_win++;
break;
}
}
else if (j <= 8 && i <= 8 && R[j][i] != 0 && (R[j][i] == R[j + 1][i + 1] && R[j][i] == R[j + 2][i + 2] && R[j][i] == R[j + 3][i + 3] && R[j][i] == R[j + 4][i + 4])) {//the checking for the \ situation.
if (R[j][i] == 1) {
playerO_win++;
break;
}
else {
playerX_win++;
break;
}
}
else if ((j >= 4 || i >= 4 || i <= 8) && R[j][i] != 0 && (R[j][i] == R[j - 1][i + 1] && R[j][i] == R[j - 2][i + 2] && R[j][i] == R[j - 3][i + 3] && R[j][i] == R[j - 4][i + 4])) {//the checking for the / situation
if (R[j][i] == 1) {
playerO_win++;
break;
}
else {
playerX_win++;
break;
}
}
for (int i = 0; i < num; i++) {//the loop for checking the draw
for (int j = 0; j < num; j++) {//this loop will check for every time compilation.
if (R[j][i] == 0)//when there are any empty block then the check_draw will adding, the draw situation is the check_draw be 0
check_draw++;
}
}
if (check_draw == 0) {//when the check_draw equal to 0 which mean the situation is no empty block
draw++;
break;
}
}
if (playerO_win != 0 || playerX_win != 0 || draw == 1)//break the second loop
break;
}
if (playerO_win == 1 && playerX_win == 0) {// when the player win print the block game again and print out the win statement
print_table(R);
cout << "player O wins!" << endl;
break;
}
else if (playerX_win == 1 && playerO_win == 0) {//the other player win the game
print_table(R);
cout << "player X wins!" << endl;
break;
}
else if (draw == 1) {//the draw block game print
print_table(R);
cout << "Draw game!" << endl;
break;
}
player = check_player(player);
} while (1);//in fact it is no need for the loop statement, because most of the situation will have a break statement for out of the loop
return 0;
}
Here's how I would implement it probably based on your initial implementation:
#include <iostream>
#include <iomanip>
#include <cstdlib>
using namespace std;
#define SIZE 10
#define LINE_LENGTH 4
#define COMPUTER_O_PLAYER true
#define COMPUTER_X_PLAYER false
void print_board(unsigned char x[SIZE][SIZE]) {
cout << " ";
for (int i = 0; i < SIZE; i++) { // The loop that use to print out the english character row.
cout << (char) ('A' + i) << " ";
}
cout << endl;
for (int i = 0; i < SIZE; i++) {
cout << setw(2) << i; // Print out the row number.
for (int j = 0; j < SIZE; j++) {//print out the board game.
if (x[i][j] == 0) { // Unoccupied tile.
cout << " .";
} else if (x[i][j] == 1) { // The tile belongs to X.
cout << " X";
} else { // The tile belongs to O.
cout << " O";
}
}
cout << endl;
}
}
void get_position(int &x, int &y, bool player, unsigned char board[SIZE][SIZE]) {
char eng;
// The loop that ask for the user input the location.
do {
cout << "Player " << (player ? "X" : "O") << ", make a move: ";
cin >> eng;
y = toupper(eng) - 'A';
cin >> x;
if (!(x >= 0 && x < SIZE) || !(y >= 0 && y < SIZE) || board[x][y] != 0) {
// When the input wrong, output the statement to ask another input and loop again.
cout << "Invalid input, Try again!" << endl;
continue;
} else { // If no problem then this input loop is break and jump to the next statement.
break;
}
} while (true);
}
void get_random_position(int &x, int &y, bool player, unsigned char board[SIZE][SIZE]) {
do {
x = rand() % SIZE;
y = rand() % SIZE;
} while ((!(x >= 0 && x < SIZE) || !(y >= 0 && y < SIZE) || board[x][y] != 0));
cout << "Player " << (player ? "X" : "O") << " chose: " << (char) ('A' + y) << x << endl;
}
unsigned int
count_in_direction(unsigned char board[SIZE][SIZE], unsigned int x, unsigned int y, short int m_x, short int m_y) {
unsigned int count = 0;
unsigned char tile = board[x][y];
while (((x + m_x >= 0) && (x + m_x < SIZE)) && ((y + m_y >= 0) && (y + m_y < SIZE)) &&
(board[x + m_x][y + m_y] == tile)) {
x += m_x;
y += m_y;
count++;
}
return count;
}
bool full_line(unsigned char board[SIZE][SIZE], unsigned int x, unsigned int y) {
const short int directions[4][2] = {{1, 0},
{1, -1},
{0, 1},
{1, 1}};
for (const auto &direction : directions) {
if (LINE_LENGTH - 1 <= (count_in_direction(board, x, y, direction[0], direction[1]) +
count_in_direction(board, x, y, -direction[0], -direction[1])))
return true;
}
return false;
}
int main() {
// The variable that for user input or checking the game state.
unsigned char board[SIZE][SIZE] = {0};
int x, y;
bool player = true;
bool draw;
srand(time(nullptr));
// Run the game.
do {
print_board(board);
if ((player && COMPUTER_X_PLAYER) || (!player && COMPUTER_O_PLAYER)) {
get_random_position(x, y, player, board);
} else {
get_position(x, y, player, board);
}
board[x][y] = player ? 1 : 2;
if (full_line(board, x, y)) {
print_board(board);
cout << "player " << (player ? "X" : "O") << " wins!" << endl;
break;
}
draw = true;
for (int k = 0; (k < SIZE) && draw; k++) {
for (int l = 0; (l < SIZE) && draw; l++) {
if (board[k][l] == 0) draw = false;
}
}
if (draw) {
print_board(board);
cout << "Draw game!" << endl;
break;
}
player = !player;
} while (true);
return 0;
}
Please take a deep look in this implementation and internalize its approach, it also support both players as user, user and computer, and both computer.
Some insights:
Don't use long if ... else when there are simpler ways.
Use the correct data types for variables.
Use indicative variables naming.
Use loops where possible, again, not long if ... else.
Keep the code well formatted.
Use #define to define global constants to use, for easier changes later and readability.
You can indeed use rand, but you don't need to get a character, you can get an index straight away and avoid the conversion.

C++ TicTacToe problems

I am trying to learn C++ and I have made litte tictactoe game but somethings wrong. I've tried to make the winner class both a void and a bool. But when I type in one coordinate it preforms the class. For making it simple you can only win if the 3 on top is O. Whats wrong?
SO if I input: 0 0 it says winner
Here's the code:
#include <iostream>
const int rows = 3;
const int elements = 3;
const char Ochar = 'O';
char board[rows][elements];
void Clear()
{
for (int i = 0; i < rows; i++)
{
for (int j = 0; j < elements; j++)
{
board[i][j] = 0;
}
}
}
void Show()
{
for (int i = 0; i < rows; i++)
{
for (int j = 0; j < elements; j++)
{
std::cout << " " << board[i][j] << " |";
}
std::cout << std::endl;
std::cout << "------------" << std::endl;
}
}
bool PlayerAttack(int x, int y)
{
if (board[x][y] == 0)
{
board[x][y] = Ochar;
return true;
}
return false;
}
void Winner()
{
if (board[0][0], board[0][1], board[0][2] = 'O')
{
std::cout << "Winner";
}
}
int main()
{
Clear();
Show();
int pos1 = 0;
int pos2 = 0;
while (1)
{
std::cout << "Please input a coordinate: "; std::cin >> pos1 >> pos2; std::cout << std::endl;
PlayerAttack(pos1, pos2);
Show();
Winner();
}
}
This line does not do what you think it does
if (board[0][0], board[0][1], board[0][2] = 'O')
You'd have to do
if (board[0][0] == 'O' && board[0][1] == 'O' && board[0][2] == 'O')
To use your Winner function to break your loop
bool Winner()
{
// You'll obviously have to check more than just this row
if (board[0][0] == 'O' && board[0][1] == 'O' && board[0][2] == 'O')
{
std::cout << "Winner";
return true;
}
return false;
}
Then in main
int main()
{
Clear();
Show();
int pos1 = 0;
int pos2 = 0;
bool winner = false;
while (!winner)
{
std::cout << "Please input a coordinate: "; std::cin >> pos1 >> pos2; std::cout << std::endl;
PlayerAttack(pos1, pos2);
Show();
winner = Winner(); // Use the returned bool
}
}

Tic tac toe game code

Good evening everyone, could anyone point me in the direction I need to go to get this code for a simple game of tic tac toe operational? I feel it is very close but I cannot get it to behave properly. Also, what could I use instead of break commands under the drawBoard command? Thanks in advance..
#include <iostream>
// This program allows user(s) to play a game of tic-tac-toe.
using namespace std;
// constants
const char SIGIL[3] = { '.', 'X', 'O' };
// prototypes
int winner(int board[3][3]);
void drawBoard(int board[3][3]);
bool isMoveLegal(int board[3][3]);
bool isGameOver(int board[3][3]);
// return 1 if player 1 'X' has won
// return 2 if player 2 'O' has won
// return 0 if neither player has won
int winner(int board[3][3]){
int win = 0;
// Checks for:
// X X X
for (int i = 0; i < 3; i++)
if (board[i][0] == board[i][1] && board[i][1] == board[i][2])
win = board[i][0];
// Checks for:
// X
// X
// X
for (int i = 0; i < 3; i++)
if (board[0][i] == board[1][i] && board[1][i] == board[2][i])
win = board[0][i];
// Checks for:
// X X
// X or X
// X X
if ((board[0][0] == board[1][1] && board[1][1] == board[2][2]) ||
(board[0][2] == board[1][1] && board[1][1] == board[2][0]))
win = board[1][1];
return win;
}
// using this board as a guide
// draw the board using "." for empty squares
// or 'X' or 'O' for player 1 or player 2
void drawBoard(int board[3][3]){
cout << " 0 1 2" << endl;
for (int i = 0; i < 3; i++){
cout << i ;
for (int j = 0; j < 3; j++){
cout.width(3);
switch (board[i][j])
{
case 0:{
cout << ".";
}break; case 1:{
cout << "X";
}break;
case 2:{
cout << "0";
}break;
default:
break;
}
} cout << endl;
}
}
// return false if row or column are out of bounds
// or if that spot on the board is already taken
// otherwise return true
bool isMoveLegal(int board[3][3], int row, int column){
if (row >= 0 && row <= 3 && column <= 3 && column >= 0) {
if (board[row][column] == 0)
return true;
else return false;
}
return false;
}
// if any player has three in a row or if the board is full
// return true otherwise return false
bool isGameOver(int board[3][3]){
if (winner(board) == 1 || winner(board) == 2) return true;
for (int r = 0; r <= 2; r++)
for (int c = 0; c <= 2; c++)
if (board[r][c] == 0)
return false;
return true;
}
int main(){
int board[3][3] = { { 0 } }; // 0 for empty square, 1 or 2 for taken squares
int player = 1;
int row, column, result;
bool legalMove;
// starting board
drawBoard(board);
while (!isGameOver(board)){
cout << "Player " << player << "(" << SIGIL[player] << "), your move?";
cin >> row >> column;
legalMove = isMoveLegal(board, row, column);
while (!legalMove){
cout << "Player " << player << "(" << SIGIL[player] << "), your move?";
cin >> row >> column;
legalMove = isMoveLegal(board, row, column);
}
board[row][column] = player;
drawBoard(board);
player = 3 - player;
}
// game over
result = winner(board);
if (result == 0){
cout << "Tie Game" << endl;
}
else {
cout << "Player " << result << "(" << SIGIL[result] << ") wins!" << endl;
}
return 0;
}
This piece of code will go out of bounds:
bool isMoveLegal(int board[3][3], int row, int column){
if (row >= 0 && row <= 3 && column <= 3 && column >= 0) {
if (board[row][column] == 0)
return true;
else return false;
}
Remember that arrays are 0-indexed, so it should be:
bool isMoveLegal(int board[3][3], int row, int column){
if (row >= 0 && row < 3 && column < 3 && column >= 0) {
if (board[row][column] == 0)
return true;
else return false;
}
Your break statements in drawBoard are for the switch statement, not a loop. They are okay, however, you should use board[i][j] as an index into SIGIL:
// constants
const char SIGIL[3] = { '.', 'X', 'O' };
// ...
void drawBoard(int board[3][3])
{
cout << " 0 1 2\n";
for (int i = 0; i < 3; ++i)
{
cout << i ;
for (int j = 0; j < 3; ++j)
{
cout << SIGIL[board[i][j]] << " ";
}
cout << endl;;
}
}

Negamax implementation doesn't appear to work with tic-tac-toe

I've implemented Negamax as it can be found on wikipedia, which includes alpha/beta pruning.
However, it seems to favor a losing move, which is an invalid result to my knowledge.
The game is Tic-Tac-Toe, I've abstracted most of the game play so it should be rather easy to spot an error within the algorithm.
#include <list>
#include <climits>
#include <iostream>
//#define DEBUG 1
using namespace std;
struct Move {
int row, col;
Move(int row, int col) : row(row), col(col) { }
Move(const Move& m) { row = m.row; col = m.col; }
};
struct Board {
char player;
char opponent;
char board[3][3];
Board() { }
void read(istream& stream) {
stream >> player;
opponent = player == 'X' ? 'O' : 'X';
for(int row = 0; row < 3; row++) {
for(int col = 0; col < 3; col++) {
char playa;
stream >> playa;
board[row][col] = playa == '_' ? 0 : playa == player ? 1 : -1;
}
}
}
void print(ostream& stream) {
for(int row = 0; row < 3; row++) {
for(int col = 0; col < 3; col++) {
switch(board[row][col]) {
case -1:
stream << opponent;
break;
case 0:
stream << '_';
break;
case 1:
stream << player;
break;
}
}
stream << endl;
}
}
void do_move(const Move& move, int player) {
board[move.row][move.col] = player;
}
void undo_move(const Move& move) {
board[move.row][move.col] = 0;
}
bool isWon() {
if (board[0][0] != 0) {
if (board[0][0] == board[0][1] &&
board[0][1] == board[0][2])
return true;
if (board[0][0] == board[1][0] &&
board[1][0] == board[2][0])
return true;
}
if (board[2][2] != 0) {
if (board[2][0] == board[2][1] &&
board[2][1] == board[2][2])
return true;
if (board[0][2] == board[1][2] &&
board[1][2] == board[2][2])
return true;
}
if (board[1][1] != 0) {
if (board[0][1] == board[1][1] &&
board[1][1] == board[2][1])
return true;
if (board[1][0] == board[1][1] &&
board[1][1] == board[1][2])
return true;
if (board[0][0] == board[1][1] &&
board[1][1] == board[2][2])
return true;
if (board[0][2] == board [1][1] &&
board[1][1] == board[2][0])
return true;
}
return false;
}
list<Move> getMoves() {
list<Move> moveList;
for(int row = 0; row < 3; row++)
for(int col = 0; col < 3; col++)
if (board[row][col] == 0)
moveList.push_back(Move(row, col));
return moveList;
}
};
ostream& operator<< (ostream& stream, Board& board) {
board.print(stream);
return stream;
}
istream& operator>> (istream& stream, Board& board) {
board.read(stream);
return stream;
}
int evaluate(Board& board) {
int score = board.isWon() ? 100 : 0;
for(int row = 0; row < 3; row++)
for(int col = 0; col < 3; col++)
if (board.board[row][col] == 0)
score += 1;
return score;
}
int negamax(Board& board, int depth, int player, int alpha, int beta) {
if (board.isWon() || depth <= 0) {
#if DEBUG > 1
cout << "Found winner board at depth " << depth << endl;
cout << board << endl;
#endif
return player * evaluate(board);
}
list<Move> allMoves = board.getMoves();
if (allMoves.size() == 0)
return player * evaluate(board);
for(list<Move>::iterator it = allMoves.begin(); it != allMoves.end(); it++) {
board.do_move(*it, -player);
int val = -negamax(board, depth - 1, -player, -beta, -alpha);
board.undo_move(*it);
if (val >= beta)
return val;
if (val > alpha)
alpha = val;
}
return alpha;
}
void nextMove(Board& board) {
list<Move> allMoves = board.getMoves();
Move* bestMove = NULL;
int bestScore = INT_MIN;
for(list<Move>::iterator it = allMoves.begin(); it != allMoves.end(); it++) {
board.do_move(*it, 1);
int score = -negamax(board, 100, 1, INT_MIN + 1, INT_MAX);
board.undo_move(*it);
#if DEBUG
cout << it->row << ' ' << it->col << " = " << score << endl;
#endif
if (score > bestScore) {
bestMove = &*it;
bestScore = score;
}
}
if (!bestMove)
return;
cout << bestMove->row << ' ' << bestMove->col << endl;
#if DEBUG
board.do_move(*bestMove, 1);
cout << board;
#endif
}
int main() {
Board board;
cin >> board;
#if DEBUG
cout << "Starting board:" << endl;
cout << board;
#endif
nextMove(board);
return 0;
}
Giving this input:
O
X__
___
___
The algorithm chooses to place a piece at 0, 1, causing a guaranteed loss, do to this trap(nothing can be done to win or end in a draw):
XO_
X__
___
I'm pretty sure the game implementation is correct, but the algorithm should be aswell.
EDIT: Updated evaluate and nextMove.
EDIT2: Fixed first problem, there still seem to be bugs though
Your evaluate function counts the empty spaces, and does not recognize a winning board.
EDIT:
There's also a relatively minor problem in nextMove. The line should be
int score = -negamax(board, 0, -1, INT_MIN + 1, INT_MAX);
Fix that (and evaluate), and the code chooses the right move.
EDIT:
This fixes it:
if (board.isWon() || depth <= 0) {
#if DEBUG > 1
cout << "Found winner board at depth " << depth << endl;
cout << board << endl;
#endif
return -100;
}
Almost all of these problems stem from not being clear about the meaning of score. It is from the point of view of player. If negamax is evaluating the position of player 1, and player 1 cannot win, the score should be low (e.g. -100); if negamax is evaluating the position of player -1, and player -1 cannot win, the score should be low (e.g. -100). If evaluate() can't distinguish the players, then returning a score of player * evaluate(board) is just wrong.
isWon returns true for both a win or a loss of the player. That can't be helping.
There seems to be something funny with the use of player.
Your toplevel loop calls "board.do_move(*it, 1);" then calls negamax with player=1.
Then negamax will call "board.do_move(*it, player);", so it looks like the first player is effectively getting 2 moves.