How do you dynamically allocate a matrix?

Question

How do you dynamically allocate a 2D matrix in C++? I have tried based on what I already know:

#include 

int main(){
    int rows;
    int c         


        

Answer 1

I have this grid class that can be used as a simple matrix if you don't need any mathematical operators.

/**
 * Represents a grid of values.
 * Indices are zero-based.
 */
template
class GenericGrid
{
    public:
        GenericGrid(size_t numRows, size_t numColumns);

        GenericGrid(size_t numRows, size_t numColumns, const T & inInitialValue);

        const T & get(size_t row, size_t col) const;

        T & get(size_t row, size_t col);

        void set(size_t row, size_t col, const T & inT);

        size_t numRows() const;

        size_t numColumns() const;

    private:
        size_t mNumRows;
        size_t mNumColumns;
        std::vector mData;
};


template
GenericGrid::GenericGrid(size_t numRows, size_t numColumns):
    mNumRows(numRows),
    mNumColumns(numColumns)
{
    mData.resize(numRows*numColumns);
}


template
GenericGrid::GenericGrid(size_t numRows, size_t numColumns, const T & inInitialValue):
    mNumRows(numRows),
    mNumColumns(numColumns)
{
    mData.resize(numRows*numColumns, inInitialValue);
}


template
const T & GenericGrid::get(size_t rowIdx, size_t colIdx) const
{
    return mData[rowIdx*mNumColumns + colIdx];
}


template
T & GenericGrid::get(size_t rowIdx, size_t colIdx)
{
    return mData[rowIdx*mNumColumns + colIdx];
}


template
void GenericGrid::set(size_t rowIdx, size_t colIdx, const T & inT)
{
    mData[rowIdx*mNumColumns + colIdx] = inT;
}


template
size_t GenericGrid::numRows() const
{
    return mNumRows;
}


template
size_t GenericGrid::numColumns() const
{
    return mNumColumns;
}