how to return 2d array?

[jNc]

Know how to return 1d array, can not find solution for 2d array
Cant use vector

[kbw]

Know how to return 1d array

You probably just know how to return the pointer, if you can't return a higher dimension array.

The trick is to return an object. So define your 2D array as an object; you can use std::array<std::array<T, NCOLS>, NROWS>, or a vector equivalent or a struct/class. Then just return that.

If you stick with pointers, you'll loose dimension sizes.

e.g.

#include <vector>
#include <iostream>

using int_d2array_t = std::vector<std::vector<int>>;

int_d2array_t create_2darray(size_t nrows, size_t ncols, int val = -1) {
    return int_d2array_t( nrows, std::vector<int>(ncols, val) );
}

int main() {
    constexpr size_t nrows{12};
    constexpr size_t ncols{6};
    auto int2d = create_2darray(nrows, ncols);

    std::cout << "nrows=" << int2d.size()
        << " ncols=" << int2d[0].size()
        << '\n';
}

EDIT: Just saw this bit,

Cant use vector

Is this homework?

[malibor]

don't return 2D array, instead pass it as a reference to function parameter.

[jonnin]

if you know the dimensions (compile time constant 2d array?) you can return it as 1d and cast it back with some ugly tricks. But that is so very C and weird code.
There are a lot of reasons why 1d mapped to 2d is easier to work with (you manually index the 1d to make it '2d' exactly the same way C does it).

if you need to see the casting junk I can figure it out again, but its not a good idea.

[seeplus]

Know how to return 1d array, can not find solution for 2d array
Cant use vector

You can't return a c-style array of any dimensions. All you can do is return a pointer to the first element.

You can wrap an array inside of a struct and return that. But the C++ way is to either use std::vector or std:::array. Why can't you use these?

#include <iostream>

struct MyArray {
	int arr[2][3] { };
};

MyArray func1() {
	MyArray myarr;

	for (auto r : { 0, 1 })
		for (auto c : { 0, 1, 2 })
			myarr.arr[r][c] = r + c;

	return myarr;
}

int main() {
	const auto arr1 { func1() };

	for (auto r : { 0, 1 }) {
		for (auto c : { 0, 1, 2 })
			std::cout << arr1.arr[r][c] << ' ';

		std::cout << '\n';
	}
}