Two-Dimensional Arrays

Up to this point, we have created and dealt only with one-dimensional array. However, like many other programming languages, Scala also supports multidimensional arrays.

Most of the time, though, programmers work with only one-dimensional and two-dimensional arrays. Three-dimensional arrays are also used but extremely rarely, and only for some very specific cases (e.g., working with images). However, you can also create n-dimensional arrays in Scala where n can be pretty large.

What is a 2D Array?

Once again, in order to work with 2D arrays, we have to understand what they actually are.

It can be easily visualized as a table or a grid consisting of rows and columns. Basically, you can think of a 2D array as a matrix with m rows and n columns, where m and n are positive integers.

Let's take a look at the general syntax of declaring a 2D array variable in Scala:

Main


              1
            
var arrayName = Array.ofDim[dataType](m, n)

The ofDim method is a method which creates an array where each element is an array itself, allowing for multiple dimensions. Once again, arrayName is simply a variable name, dataType is the data type of the array elements, m and n are the number of rows and columns, respectively.

Similarly to 1D arrays, we can declare a 2D array with predefined elements. Here's an example:

Main


              12345
            
var matrix = Array(
	Array(1, 2, 3),
	Array(4, 5, 6),
	Array(7, 8, 9),
	Array(10, 11, 12))

Here, for our 2D array we create 4 1D arrays with 3 predefined elements, so we get a 4x3 2D array.

Indexing in 2D Arrays

Let's first take a look at the visualization of the 2D array which we created in the example above:

As you can see, the indexing in 2D arrays is similar to that of 1D arrays. Basically, rows (1D arrays) are indexed by integers from 0 to n - 1 (3 in our case), where n is the number of rows, and columns from 0 to m - 1 (2 in our case), where m is the number of columns.

To access a particular element in a 2D array, we have to specify its row index and column index. For instance, the element with the value of 8 in our example has 2 and 1 as its row and column indices, respectively.

Let's now take a look at the code:

Main


              12345678910
            
object Main {
  def main(args: Array[String]): Unit = {
    var matrix = Array(
      Array(1, 2, 3),
      Array(4, 5, 6),
      Array(7, 8, 9),
      Array(10, 11, 12))
    println(matrix(2)(1))
  }
}

We can also manually fill a 2D array with elements using indices:

Main


              123456789
            
object Main {
  def main(args: Array[String]): Unit = {
    var matrix = Array.ofDim[Int](2, 2)
    matrix(0)(0) = 23
    matrix(0)(1) = 54
    matrix(1)(0) = 68
    matrix(1)(1) = 10
  }
}

Here is how we can visualize this 2x2 2D array:

Now, it's time to test our knowledge.

Everything was clear?

Thanks for your feedback!

Section 4. Chapter 4