Function call

[pacman169]

Hello,

I`m not sure if I have called function int Search(int depth) correctly on line 167. If that`s the case, it would explain why the program behaves so strangely.

#include <iostream>
#include <bitset>
#include <cstdlib>
#include <vector>

using std::cin;
using std::cout;
using std::ostream;
using std::endl;
using std::bitset;

const size_t N = 3;
typedef bitset <N*N> board;


const board wins[] = {
    board(0b111000000), board(0b000111000), board(0b000000111),    // rows
    board(0b100100100), board(0b010010010), board(0b001001001),	// cols
    board(0b100010001), board(0b001010100)	// diagonals
};

board noughts;			// bit board for first player
board crosses;			// bit board for second player


const char NOUGHT = 'O';
const char CROSS = 'X';


board combined();
ostream & print_board(ostream & stm = cout, board b = combined());

// This indicates the current player. Computer plays noughts.
bool curr_move_noughts = true;

board
combined()
{
    return noughts | crosses;
}				// combined bit board for both players

bool
valid(size_t row, size_t col)
{
    return row < N && col < N;
}

size_t
pos(size_t row, size_t col)
{
    return row * N + col;
}				// map row, col to bit position

bool
occupied(size_t row, size_t col)
{
    return valid(row, col) && combined()[pos(row, col)];
}

bool
free(size_t row, size_t col)
{
    return valid(row, col) && !occupied(row, col);
}

size_t last_move_row = -1, last_move_col = -1 ;

void make_move( size_t row, size_t col, board & b )
{
    if (free(row, col))
    {
	b[pos(row, col)] = true;
        last_move_row = row ;
        last_move_col = col ;
    } 
}

void unMake(board & b )
{
	
    
    if (valid(last_move_row, last_move_col))// if valid last_move_row, last_move_col
    {
    int row= -1;
    int col= -1;
    b[pos(row, col)] = true;
    last_move_row = -1 ;
    last_move_col = -1 ; 
    }
}

void
make_move(size_t row, size_t col)
{
    if (curr_move_noughts)
	make_move(row, col, noughts);
    else
	make_move(row, col, crosses);
}

bool
is_win(board b)
{
    for (int i = 0; i < sizeof(wins) / sizeof(wins[0]); ++i) {
	if ((wins[i] & b) == wins[i])
	    return true;
    }
    return false;
}

bool
is_win()
{
    return is_win(curr_move_noughts ? noughts : crosses);
}

// is the board full?
bool is_full(board b)
{
    static board fullboard(0b111111111);
    return b == fullboard;
}

bool is_full()
{
    return is_full(curr_move_noughts ? noughts : crosses);
}

int Evaluate()

{ 
    
 int depth;

 if (is_win (crosses))             

 {return depth-1;}

 else if (is_win (curr_move_noughts))

 {return  1-depth; }

 else   {return 0;} 
 
 

}





void
play()
{

    int row = -1;		// For player input
    int col = -1;

    for (int turns = 0; turns < 9; ++turns) {
	curr_move_noughts = !curr_move_noughts;

	if (curr_move_noughts) {
	   int Search(int depth); 		// computer plays noughts
	} else {
	    cout << "Choose a move..." << endl;
	    cout << "Enter row and col : ";
	    cin >> row >> col;
	    // dmh - note that valid rows/col are 0-2, not 1-3. If you
	    // want the user to enter 1-3 then decrement the value
	    // they enter right after they enter it
	    if (!valid(row,col)) {
		cout << "Illegal move!  Try again...\n" << endl;
	    } else {
		make_move(row, col);
	    }
	}
	print_board();
	if (is_win()) {
	    cout << "Player " << (curr_move_noughts ? NOUGHT : CROSS) << " has won!" << endl; exit(0);
	} else if (is_full()) {
	    cout << "Game ended in a tie!" << endl;
	}
    }
}



ostream & print_board(ostream & stm, board b)
{
    stm << "------\n";
    for (std::size_t i = 0; i < N; ++i) {
	for (std::size_t j = 0; j < N; ++j) {
	    const size_t
		k = pos(i, j);
	    if (b[k])
		stm << (noughts[k] ? NOUGHT : CROSS) << ' ';
	    else
		stm << ". ";
	}
	stm << '\n';
    }
    return stm << "------\n";
}

int Search(int depth)
{
  
  board b = combined();
  int score;
  int x,y;
  int bestScore = -2;
  bool bestMove = false;
  if(depth == 0) return Evaluate(); 
  for (int turns = 0; turns < 9; ++turns) {                 // loop over turns
    while (occupied(x,y));
    make_move(x, y);              
    score = -Search(depth-1);       // recursion 
    unMake(b);
    if(score > bestScore) {         
      bestScore = score;
      bestMove = (x,y);
    }
  }
  return  bestScore; 
  return  bestMove;

 }
 

			

int
main()
{
    play();
    return 0;
}

Here was some output in my tests:

Choose a move...

Enter row and col : Illegal move! Try again...


------

. . .

. . .

. . .

------

------

. . .

. . .

. . .

------

Choose a move...

Enter row and col : Illegal move! Try again...

[minomic]

No you have not called the function correctly. You have a function accepting an int as a parameter and returning an int as a result. So a correct way to use this function would be

int my_result = 0;

my_result = Search(5);

Or, in general

int my_result = Search(another_int);

I passed a int to the function, then took the result returned by the function and assigned it to an appropriate variable (i.e. an int).

[pacman169]

Ok.

If I remember right, I already tried that. Then I get error " Search was not declared in this scope".

Should I do something like

int Search(int depth);

   if (curr_move_noughts)
       {
	   int z = 0;
           z= Search(5);		// computer plays noughts
	} 
	

[minomic]

That's because the function Search is defined after the line in which you call it. So you have two possible solutions:

1. you move the entire function Search before the main
2. you put a prototype before the main and leave the definition of the function where it is. In this way you "announce" that there will be a funcion called Search that accepts a parameter, etc.

[pacman169]

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24

Choose a move... Enter row and col : 0 2

. . X . . . . . . ------ ------ . . X . . . . . . ------ Choose a move... Enter row and col : 0 1 ------ . X X . . . . . . ------ ------ . X X . . . . . . ------ Choose a move... Enter row and col :

EDIT: That didn`t work out like I was expecting...