How to pass and return a 3-Dimensional Array in C++?

In C++ a 3-dimensional array can be implemented in two ways:

• Using array (static)
• Using vector (dynamic)

Passing a static 3D array in a function: Using pointers while passing the array. Converting it to the equivalent pointer type.

char ch[2][2][2];
void display(char (*ch)[2][2]) {
    . . .
}

Program to pass a static 3D array as a parameter:

C++

// C++ code to demonstrate the above method

#include <bits/stdc++.h>
using namespace std;

// Function to show how to pass
// a 3D character array to a function
void display(char (*ch)[2][2])
{
    for (int i = 0; i < 2; i++) {
        for (int j = 0; j < 2; j++) {
            for (int k = 0; k < 2; k++) {
                cout << "ch[" << i << "][" << j << "]["
                     << k << "] = " << ch[i][j][k] << endl;
            }
        }
    }
}

// Driver code
int main()
{
    char ch[2][2][2] = { { { 'a', 'b' }, { 'c', 'd' } },
                         { { 'e', 'f' }, { 'g', 'h' } } };

    // Function call with 3D array as parameter
    display(ch);
    return 0;
}

Output

ch[0][0][0] = a
ch[0][0][1] = b
ch[0][1][0] = c
ch[0][1][1] = d
ch[1][0][0] = e
ch[1][0][1] = f
ch[1][1][0] = g
ch[1][1][1] = h

Time Complexity:   O(n³)

Auxiliary Space: O(1)

Passing 3D vector (dynamic array): When a vector is passed to a function, it can either be passed by value, where a copy of the vector is stored, or by reference, where the address of the vector is passed.

• Pass by value: 

void function(vector <vector <vector < char >>> ch) {
    . . .
}

• Pass by reference (Better):

void function(vector< vector < vector < char>>> &ch) {
    . . .
}

Program to pass a dynamic 3D array as a parameter:

C++

// C++ code to demonstrate the initialization
// and passing as a parameter (passed as reference)

#include <bits/stdc++.h>
using namespace std;

// Parameter passed as reference
void display(vector<vector<vector<char> > >& ch)
{
    for (int i = 0; i < 2; i++) {
        for (int j = 0; j < 2; j++) {
            for (int k = 0; k < 2; k++) {
                cout << "ch[" << i << "][" << j << "]["
                     << k << "] = " << ch[i][j][k] << endl;
            }
        }
    }
}

int main()
{
    vector<vector<vector<char> > > ch
        = { { { 'a', 'b' }, { 'c', 'd' } },
            { { 'e', 'f' }, { 'g', 'h' } } };

    // Function to call function by passing as parameter
    display(ch);
    return 0;
}

Output

ch[0][0][0] = a
ch[0][0][1] = b
ch[0][1][0] = c
ch[0][1][1] = d
ch[1][0][0] = e
ch[1][0][1] = f
ch[1][1][0] = g
ch[1][1][1] = h

Time Complexity:  O(n³)

Auxiliary Space: O(1)

Returning a 3D array: A static array cannot be returned from a function in C++. So we have to pass a 3D vector from a function to get the functionality of returning a 3D array.

vector <vector< vector <char>>> fun() {
    vector <vector< vector <char>>> ch;
    . . .
    return ch;
}