Passing Multidimensional Arrays to Functions in C++

In C++, passing multidimensional arrays to functions can be achieved through various methods. This tutorial will cover four approaches: passing by reference, passing by pointer, using templates, and passing a pointer to a pointer.

Passing by Reference

When passing a multidimensional array by reference, the function receives a direct alias of the original array. This method is safe because it ensures that the dimensions of the array are preserved.

template <size_t rows, size_t cols>
void process_2d_array_template(int (&array)[rows][cols]) {
    // Access elements using array[i][j]
}

int main() {
    int a[5][10];
    process_2d_array_template(a);
    return 0;
}

Passing by Pointer

Passing a multidimensional array by pointer involves passing the address of the first element of the array. The function receives a pointer to an array, which can be used to access elements.

void process_2d_array_pointer(int (*array)[5][10]) {
    // Access elements using (*array)[i][j]
}

int main() {
    int a[5][10];
    process_2d_array_pointer(&a);  // Notice the address-of operator (&)
    return 0;
}

Using Templates

Templates can be used to create functions that accept multidimensional arrays of varying sizes. This approach provides flexibility and ensures type safety.

template <typename TwoD>
void myFunction(TwoD& myArray) {
    // Access elements using myArray[i][j]
}

int main() {
    double anArray[10][10];
    myFunction(anArray);
    return 0;
}

Passing a Pointer to a Pointer

Passing a pointer to a pointer involves passing the address of a pointer that points to the first element of each row. This approach requires careful memory management and is generally less safe than other methods.

void process_pointer_2_pointer(int** array, size_t rows, size_t cols) {
    // Access elements using array[i][j]
}

int main() {
    int* b[5];  // Surrogate array of pointers
    for (size_t i = 0; i < 5; ++i) {
        b[i] = new int[10];
    }
    process_pointer_2_pointer(b, 5, 10);
    return 0;
}

Comparison of Approaches

| Approach | Safety | Flexibility |
| — | — | — |
| Passing by Reference | High | Medium |
| Passing by Pointer | Medium | Medium |
| Using Templates | High | High |
| Passing a Pointer to a Pointer | Low | High |

In conclusion, passing multidimensional arrays to functions in C++ can be achieved through various methods. The choice of approach depends on the specific requirements of the problem and the trade-offs between safety, flexibility, and performance.