井字游戏代码故障

Question

I am a really beginner of C++, looking for help for this code. I can not figure out why this code always returns " You can not choose the cell. Choose again!" What makes this code wrong? Could u pls help?

#include <iostream>
#include <string>

void playTTT();
void outBoard(char board[3][3]);
char nextplay(char symbol);
bool checkResult(char board[3][3], char symbol, int plays);
bool check(int row, int col);



int main()
{
    using namespace std;

    cout << "Let's play Tic Tac Toe!" << endl;
    cout << endl;

    playTTT();

    char yn = 'a';



    return 0;
}

//Where the game starts. Sets up board and runs 9 plays
void playTTT()
{
    using namespace std;

    char board[3][3] =
    {
        { ' ', ' ', ' ', },{ ' ', ' ', ' ', },{ ' ', ' ', ' ' }
    };
    outBoard(board);

    char symbol = ' ';

    for (int count = 1; count < 10; count++)
    {
        if (!(count % 2)) {
            symbol = 'O';
        }
        else {
            symbol = 'X';
        }

        nextplay(symbol);

        outBoard(board);

        if (count > 4)
            if (checkResult(board, symbol, count)) break;
    }
}

//Takes next move and checks for errors
char nextplay(char symbol) {
    using namespace std;
    char board[3][3];
    char answer = false;
    int row, col;

    cout << "Player" << symbol << " Enter a row and column" << endl;
    cin >> row >> col;
    row--, col--;
    answer = check(row, col);
    if (answer == true) {
        cout << " You can not choose the cell. Choose again!" << endl;
    }
    else {
        return board[row][col] = symbol;
    }
}


bool check(int row, int col) {
    using namespace std;

    char board[3][3];
    if (board[row][col] == 'X' || 'O'){
        return true;
    }
    else{
        cout << "Going through Check";
        return false;
    }

}

//Output the board
void outBoard(char x[3][3])
{
    using namespace std;

    cout << "  1   2   3 \n";
    cout << "1 " << x[0][0] << " | " << x[0][1] << " | " << x[0][2] << " \n";
    cout << " ---+---+---\n";
    cout << "2 " << x[1][0] << " | " << x[1][1] << " | " << x[1][2] << " \n";
    cout << " ---+---+---\n";
    cout << "3 " << x[2][0] << " | " << x[2][1] << " | " << x[2][2] << " \n";
}

//Check to see if a player win or even
bool checkResult(char board[3][3], char symbol, int count)
{
    using namespace std;

    bool winner = false;

    //Check vertical and horizontal
    for (int k = 0; k < 3; k++)
    {
        if (board[k][0] == symbol && board[k][1] == symbol && board[k][2] == symbol)
            winner = true;
        if (board[0][k] == symbol && board[1][k] == symbol && board[2][k] == symbol)
            winner = true;
    }

    //Check diagonal
    if (board[0][0] == symbol && board[1][1] == symbol && board[2][2] == symbol)
        winner = true;
    if (board[2][0] == symbol && board[1][1] == symbol && board[0][2] == symbol)
        winner = true;

    if (winner)
        cout << "Congratulations! The winner is " << symbol << "!!" << endl;
    if (!(winner) && (count == 9))
        cout << "The result is even." << endl;

    return winner;
}

Answer 1

You are incorrectly checking for an 'X' or 'O'

The line

if (board[row][col] == 'X' || 'O'){

should be

if (board[row][col] == 'X' || board[row][col] == 'O'){

Due to operator precedence , == is being evaluated before ||.

board[row][col] == 'X'

may or not be true, but

(true or false) || 'O'

is always true.