Multi-Dimensional Arrays

In C++, multi-dimensional arrays are basically arrays of arrays. They are used to hold structured data, such as a table with rows and columns. A common example is an array that depicts a matrix, with multiple rows and columns of data.

Two-Dimensional Arrays

The two-dimensional array (2D array) is the most simple type of multi-dimensional array. Consider it a grid or a table with rows and sections. You must indicate the number of rows and columns when declaring a 2D array:

int myArray[3][4]; // This declares an integer 2D array with 3 rows and 4 columns

Each element in the 2D array can be accessed using its row and column index:

myArray[0][0] = 1; // This sets the first row, first column element to the value 1

You can also initialize a 2D array when declaring it:

// This initializes the elements of our 2D array
int myArray[3][4] = {
    {1, 2,  3,  4},
    {5, 6,  7,  8},
    {9, 10, 11, 12}
};

Multi-Dimensional Arrays

C++ allows you to declare arrays with more than two dimensions by simply adding more square brackets [].

Declaring a three-dimensional (3D) array

int my3dArray[2][3][4];

This declares an integer 3D array with dimensions

  • "depth" or "layers" (size: 2)
  • "rows" (size: 3)
  • "columns" (size: 4)

A 3D array can be thought of as a collection of tables or matrices. In this case, we have two layers, each with a table with three rows and four columns.

Just like with 2D arrays, you can access and modify the elements using their indices:

// This sets the first layer, second row, third column element to the value 42
my3dArray[0][1][2] = 42;

You can initialize a multi-dimensional array when declaring it:

// This initializes the elements of 3D array
int my3dArray[2][3][4] = {
    {
        {1, 2,  3,  4},
        {5, 6,  7,  8},
        {9, 10, 11, 12}
    },
    {
        {13, 14, 15, 16},
        {17, 18, 19, 20},
        {21, 22, 23, 24}
    }
};

Looping over Multi-Dimensional Arrays

To iterate over all elements in a multi-dimensional array, you can use nested loops. The outer loop iterates over one dimension (e.g., rows), while an inner loop iterates over another (e.g., columns)

Example

XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX

The same concept applies to arrays with more dimensions, simply add more nested loops as needed.

Conclusion

Multi-dimensional arrays make it easy to work with structured data in C++. Using indices and loops, they are simple to access and manipulate. However, larger arrays may consume significant memory resources, so when working with multi-dimensional arrays, it is important to consider the size and efficiency.