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15. C++ Multidimensional Arrays

C++ Multidimensional Arrays

In this article, you'll learn about multi-dimensional arrays in C++. More specifically, how to declare them, access them and use them efficiently in your program.

Working with C++ multidimensional arrays

In C++, you can create an array of an array known as multi-dimensional array. For example:
int x[3][4];
Here, x is a two dimensional array. It can hold a maximum of 12 elements.
You can think this array as table with 3 rows and each row has 4 columns as shown below.
Elements in two dimensional array in C++ Programming
Three dimensional array also works in a similar way. For example:
float x[2][4][3];
This array x can hold a maximum of 24 elements. You can think this example as: Each of the 2 elements can hold 4 elements, which makes 8 elements and each of those 8 elements can hold 3 elements. Hence, total number of elements this array can hold is 24.

Multidimensional Array Initialisation

You can initialise a multidimensional array in more than one way.

Initialisation of two dimensional array

int test[2][3] = {2, 4, -5, 9, 0, 9};
Better way to initialise this array with same array elements as above.
int  test[2][3] = { {2, 4, 5}, {9, 0 0}};

Initialisation of three dimensional array

int test[2][3][4] = {3, 4, 2, 3, 0, -3, 9, 11, 23, 12, 23, 
                 2, 13, 4, 56, 3, 5, 9, 3, 5, 5, 1, 4, 9};
Better way to initialise this array with same elements as above.
int test[2][3][4] = { 
                     { {3, 4, 2, 3}, {0, -3, 9, 11}, {23, 12, 23, 2} },
                     { {13, 4, 56, 3}, {5, 9, 3, 5}, {3, 1, 4, 9} }
                 };

Example 1: Two Dimensional Array

C++ Program to display all elements of an initialised two dimensional array.
#include <iostream>
using namespace std;

int main()
{
    int test[3][2] =
    {
        {2, -5},
        {4, 0},
        {9, 1}
    };

    // Accessing two dimensional array using
    // nested for loops
    for(int i = 0; i < 3; ++i)
    {
        for(int j = 0; j < 2; ++j)
        {
            cout<< "test[" << i << "][" << j << "] = " << test[i][j] << endl;
        }
    }

    return 0;
}
Output
test[0][0] = 2
test[0][1] = -5
test[1][0] = 4
test[1][1] = 0
test[2][0] = 9
test[2][1] = 1

Example 2: Two Dimensional Array

C++ Program to store temperature of two different cities for a week and display it.
#include <iostream>
using namespace std;

const int CITY = 2;
const int WEEK = 7;

int main()
{
    int temperature[CITY][WEEK];

    cout << "Enter all temperature for a week of first city and then second city. \n";

    // Inserting the values into the temperature array
    for (int i = 0; i < CITY; ++i)
    {
        for(int j = 0; j < WEEK; ++j)
        {
            cout << "City " << i + 1 << ", Day " << j + 1 << " : ";
            cin >> temperature[i][j];
        }
    }

    cout << "\n\nDisplaying Values:\n";

    // Accessing the values from the temperature array
    for (int i = 0; i < CITY; ++i)
    {
        for(int j = 0; j < WEEK; ++j)
        {
            cout << "City " << i + 1 << ", Day " << j + 1 << " = " << temperature[i][j] << endl;
        }
    }

    return 0;
}
Output
Enter all temperature for a week of first city and then second city. 
City 1, Day 1 : 32
City 1, Day 2 : 33
City 1, Day 3 : 32
City 1, Day 4 : 34
City 1, Day 5 : 35
City 1, Day 6 : 36
City 1, Day 7 : 38
City 2, Day 1 : 23
City 2, Day 2 : 24
City 2, Day 3 : 26
City 2, Day 4 : 22
City 2, Day 5 : 29
City 2, Day 6 : 27
City 2, Day 7 : 23


Displaying Values:
City 1, Day 1 = 32
City 1, Day 2 = 33
City 1, Day 3 = 32
City 1, Day 4 = 34
City 1, Day 5 = 35
City 1, Day 6 = 36
City 1, Day 7 = 38
City 2, Day 1 = 23
City 2, Day 2 = 24
City 2, Day 3 = 26
City 2, Day 4 = 22
City 2, Day 5 = 29
City 2, Day 6 = 27
City 2, Day 7 = 23

Example 3: Three Dimensional Array

C++ Program to Store value entered by user in three dimensional array and display it.
#include <iostream>
using namespace std;

int main()
{
    // This array can store upto 12 elements (2x3x2)
    int test[2][3][2];

    cout << "Enter 12 values: \n";
    
    // Inserting the values into the test array
    // using 3 nested for loops.
    for(int i = 0; i < 2; ++i)
    {
        for (int j = 0; j < 3; ++j)
        {
            for(int k = 0; k < 2; ++k )
            {
                cin >> test[i][j][k];
            }
        }
    }

    cout<<"\nDisplaying Value stored:"<<endl;

    // Displaying the values with proper index.
    for(int i = 0; i < 2; ++i)
    {
        for (int j = 0; j < 3; ++j)
        {
            for(int k = 0; k < 2; ++k)
            {
                cout << "test[" << i << "][" << j << "][" << k << "] = " << test[i][j][k] << endl;
            }
        }
    }

    return 0;
}
Output
Enter 12 values: 
1
2
3
4
5
6
7
8
9
10
11
12

Displaying Value stored:
test[0][0][0] = 1
test[0][0][1] = 2
test[0][1][0] = 3
test[0][1][1] = 4
test[0][2][0] = 5
test[0][2][1] = 6
test[1][0][0] = 7
test[1][0][1] = 8
test[1][1][0] = 9
test[1][1][1] = 10
test[1][2][0] = 11
test[1][2][1] = 12
As the number of dimension increases, the complexity also increases tremendously although the concept is quite similar


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