How to initialize 2d array using 1d arrays in C++

Question

I have the following code

int vertical[] = {0, 1};
int horizontal[] = {1, 0};
int diag1[] = {1, 1}, diag2[] = {1, -1};

int directions[][] = {vertical, horizontal, diag1, diag2};

Which gives me the following error on line 5:

Array has incomplete element type 'int []'

Thus, I'm stuck doing the following:

int directions[4][2] = {{0,1},{1,0},{1,1},{1,-1}};

How can I define directions[][] using the four 1d arrays?

How about C++ arrays: std::array? We are in 2021 with C++20 and people are still using C arrays. — Thomas Sablik
– Thomas Sablik, Commented Mar 21, 2021 at 0:34

Thomas Sablik · Accepted Answer · 2021-03-21 00:44:04Z

1

You can use std::array

#include <array>
#include <iostream>

int main() {
    std::array vertical {0, 1};
    std::array horizontal {1, 0};
    std::array diag1 {1, 1}, diag2 {1, -1};

    std::array directions {vertical, horizontal, diag1, diag2};
    for (const auto dir : directions) {
        for (const auto val : dir) {
            std::cout << val << ' ';
        }
        std::cout << '\n';
    }
}

answered Mar 21, 2021 at 0:44

Thomas Sablik

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