Accessing Elements in Nested Arrays

To access elements in a multidimensional std::array, you use multiple sets of square brackets [], one for each dimension.

Here's an example of a 2D array (an array of arrays):

1#include <array>
2#include <iostream>
3
4int main() {
5  std::array<std::array<int, 3>, 2> MyArray{
6    {
7      {1, 2, 3},
8      {4, 5, 6}
9    }
10  };
11
12  std::cout << "Bottom Right: " << MyArray[1][2];  
13}

1Bottom Right: 6

In this case, MyArray is an array that contains 2 elements, each of which is an array of 3 integers.

To access an element, the first set of [] specifies which sub-array you want, and the second set specifies the element within that sub-array. So, MyArray[1][2] accesses the 3rd element (remember, indices start at 0) of the 2nd sub-array, which is 6.

The same principle extends to higher dimensions. For example, the following is a three dimensional array (2x2x2):

1#include <array>
2#include <iostream>
3
4int main() {
5  std::array MyArray{
6    std::array{
7      std::array{1, 2},
8      std::array{3, 4}
9    },
10    std::array{
11      std::array{5, 6},
12      std::array{7, 8}
13    },
14  };
15
16  std::cout << "Value: " << MyArray[1][1][0];  
17}

1Value: 7

Here, MyArray[1][1][0] would access the 1st element of the 2nd sub-array of the 2nd sub-array of MyArray, which is 7.

Remember that each set of [] can be an expression that evaluates to an integer, not just a literal integer. For example:

1int i = 1;
2int j = 2;
3int value = MyArray[i][j];

This would access MyArray[1][2] just like in the first example.

Also note that each access (MyArray[i][j]) returns a reference to the element, which you can read from or write to.