Need to pass a pointer of a unknown sized 2d array

This is a discussion on Need to pass a pointer of a unknown sized 2d array within the C++ Programming forums, part of the General Programming Boards category; Ok, so I've read allot about this problem but still cant figure it out. Basically Im making a Tetris game, ...

  1. #1
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    Need to pass a pointer of a unknown sized 2d array

    Ok, so I've read allot about this problem but still cant figure it out.

    Basically Im making a Tetris game, I have a function 'getRandomPiece()' which I would like to return a random Tetris piece which is a 2d array. Problem is, not all pieces are the same dimensions (same width and height).

    So after allot of reading it seems c++ cant return an array.

    So then ill try passing a pointer to store the array. The problem with this is c++ wants me to declare the size of the array in the parameter which I dont know what its going to be yet.

    Ideally in Java I can just go

    Code:
    int[][] getRandomPiece(){
          //Random logic
         int[][] arr = {{1,1,0},
                             {0,1,1}};
          return arr;
    }
    Which is the best way to solve this problem?

  2. #2
    Registered User rynoon's Avatar
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    I'd just use a vector of vectors and avoid this entire headache.

  3. #3
    l'Anziano DavidP's Avatar
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    So this array represents the shape of the random piece, then?

    I don't know how large scale this tetris game your making is, but a simple "piece" class would go a long ways to help out on such a problem. There are several ways you could approach this.

    You could make a seperate class for each type of piece, and have them all derive from the base piece class. Then each piece would automatically store a 2d array with its shape inside. For example:

    Code:
    class LSHAPE: public PIECE
    {
    private:
    
    int shape [][] = { {011}, {001}, {001} };
    ...then comes the rest of the class...
    };
    You have to keep in mind that the pieces will be rotating, and therefore this matrix wont be staying the same.

    Essentially the most states any piece could have is 4 different states, and so you could have 4 different matrixes, and then a variable that flags which matrix should be used for the display of pieces in your tetris game.

    If you dont want to hold 4 different matrixes, I think some bitwise operations could be done to "rotate" the matrix.

    Now, back to the problem at hand. If you created a seperate derived class for each piece, you could have you random logic that selects a piece, and then just return that piece (which already contains its correct matrix) instead of returning a matrix.

    Example:

    Code:
    PIECE *randomPiece ( )
    {
    
    ...random piece logic...
    
    switch ( logic result )
    {
    case LSHAPE_PIECE:
        return new LSHAPE();
    
    ...etc....
    }
    
    }
    Does this help?
    My Website

    "Circular logic is good because it is."

  4. #4
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    It does help, although in Java I have already written a algorithm to rotate a 2d array and would rather use that than pre-calculated rotations.

    I guess each class such as LShape could have its own rotate function which only rotated its own shape...

    Thanks for the ideas both of you.

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