将二维数组传递给 function 并用数字填充

Question

I'm trying to do task in C++. I need create this function:

void fillArray(std::array<std::array<int, maxColumns>, maxRows> array, size_t rows, size_t columns) {

}

Right now my example code looks like this:

#include <iostream>
#include <array>
constexpr int maxColumns = 42;
constexpr int maxRows = 334;

void fillArray(std::array<std::array<int, maxColumns>, maxRows> array, size_t rows, size_t columns) {

}


int main()
{
    
}

I need to fill the array with numbers from 1 to rows*columns starting from [0][0] and diagonally. How to declare and initialize the function with array in this example and then fill it diagonally? Any help would be greatly appreciated!

Answer 1

It should be

template <std::size_t maxColumns, std::size_t maxRows>
void fillArray(std::array<std::array<int, maxColumns>, maxRows>& array) {
// ...
}

Demo

Answer 2

Let's suppose you use a simple one-dimensional valarray (or array if you insist) of the size width * height wrapped in a class:

class Matrix
{
private:
    std::valarray<int> _data;
    int _width, _height;

public:
    Matrix(int width, int height) : _width(width), _height(height), _data(width * height)
    {
    }
}

Then you can add a member function that maps x, y coordinates to an item reference:

int& item(int x, int y) { return _data[x + _width * y]; }

... and another one for filling it diagonally like this:

void fillDiagonally(int value = 0, int step = 1)
{
    for (int i = 0; i < _height + _width; ++i) {
        // calculate starting coordinates (along left edge and then bottom edge)
        int row = i < _height ? i : _height - 1;
        int col = i < _height ? 0 : i - _height + 1;
        // move diagonally up and right until you reach margins, while filling-in values
        for (int j = 0; j < _width - col && j <= row; ++j) {
            item(col + j, row - j) = value;
            value += step;
        }
    }
}

and use it like this:

int main()
{
    Matrix m(8, 5);
    m.fillDiagonally(1);
}

This way, you don't need to pass the array as an argument, because it's a part of the class. Otherwise you would have to pass it by reference, like you were suggested above.