如何在C++中创建堆上的二维数组？

Question

我正在尝试用C++做一个国际象棋模拟。我已经创建了一个类Pieces，我想在堆上创建一个由所有块组成的二维数组。这是我的代码:国王、王后和其他人都是从碎片中派生出来的。

king = new King();
queen = new Queen();
knight = new Knight();
bishop = new Bishop();
rook = new Rook();
pawn = new Pawn();
empty = new Pieces();

Pieces* startup[64] = {rook, knight, bishop, king, queen, bishop, knight, rook,
                       pawn, pawn, pawn, pawn, pawn, pawn, pawn, pawn,
                       empty, empty, empty, empty, empty, empty, empty, empty,
                       empty, empty, empty, empty, empty, empty, empty, empty,
                       empty, empty, empty, empty, empty, empty, empty, empty,
                       empty, empty, empty, empty, empty, empty, empty, empty,
                       pawn, pawn, pawn, pawn, pawn, pawn, pawn, pawn,
                       rook, knight, bishop, king, queen, bishop, knight, rook};
Pieces* board = new Pieces[8][8];
int k = 0;
for (int i = 0; i < 8; i++) {
    for (int j = 0; j < 8; j++) {
        board[i][j] = startup[k];
        k++;
    }
}

但这给了我以下错误：

ChessBoard.cpp: In constructor ‘ChessBoard::ChessBoard()’:
ChessBoard.cpp:25: error: cannot convert ‘Pieces (*)[8]’ to ‘Pieces*’ in initialization
ChessBoard.cpp:29: error: no match for ‘operator[]’ in ‘board[i][j]’

如何在堆上成功分配一个二维数组？另外，创建一个指向块的指针数组还是创建一个块对象数组更好呢？

Answer 1

为什么你需要所有的动态分配？简单地使用64个元素的枚举数组，并在顶部添加一些伪造的2D索引。

下面是一个例子：

#include <array>
#include <iostream>

enum class piece_t
{
   EMPTY = 0, PAWN, ROOK, BISHOP, KNIGHT, QUEEN, KING
};

static const size_t WIDTH = 8, HEIGHT = 8;
struct board_t : std::array<piece_t, WIDTH*HEIGHT>
{
    board_t()
    {
        for (size_t y = 0; y < HEIGHT; y++)
            for (size_t x = 0; x < WIDTH; x++)
                operator()(x,y) = piece_t::EMPTY;
    }

    piece_t& operator()(size_t x, size_t y)
    {
        return operator[](x + y*WIDTH);
    }

    const piece_t& operator()(size_t x, size_t y) const
    {
        return operator[](x + y*WIDTH);
    }
};

std::ostream& operator<<(std::ostream& os, const piece_t& piece)
{
    switch (piece) {
        case piece_t::KING:   return (os << 'K');
        case piece_t::QUEEN:  return (os << 'Q');
        case piece_t::KNIGHT: return (os << 'N');
        case piece_t::BISHOP: return (os << 'B');
        case piece_t::ROOK:   return (os << 'R');
        case piece_t::PAWN:   return (os << 'P');
        case piece_t::EMPTY:  return (os << ' ');
        default:              return (os << '?');
    }
}

std::ostream& operator<<(std::ostream& os, const board_t& board)
{
    os << '+' << std::string(WIDTH, '-') << '+' << '\n';
    for (size_t y = 0; y < HEIGHT; y++) {
        os << '|';
        for (size_t x = 0; x < WIDTH; x++)
            os << board(x, y);
        os << '|' << '\n';
    }
    os << '+' << std::string(WIDTH, '-') << '+' << '\n';
    return os;
}

int main()
{
   board_t b;
   b(3, 5) = piece_t::KING;
   b(6, 4) = piece_t::KNIGHT;
   std::cout << b << std::endl;
   // etc.
}

Live demo

简单得多，也更安全。:-)

Answer 2

您只需要两个简单的更改。委员会的声明应为：

  Pieces (*board)[8]  = new Pieces[8][8];

换句话说，board是指向8元素数组(数组)的指针。那么作业应该是：

  board[i][j] = *startup[k];

请注意，棋盘是一个二维的棋子数组，而不是一个指针数组，这可能是您真正想要的。

Answer 3

创建电路板阵列，如下所示

Pieces** board=new Pieces*[8];
for (int i=0; i<8; i++)
{
   board[i] = new Pieces[8];
}