Arrays

Array stores multiple values of identical type.

Array size (values count) is set during initialization.

Initialization

There are couple of ways to initialize array:

Empty array

int arrayName[10];

In this case, we declare an array which can contain 10 integer numbers.

Initial values

string colors[3] = { "red", "green", "value" };

In this example an array of 3 string values is created.

Defining array size via constant

const int size = 4; int arrayName[size];

Notice that array's size cannot be set through variable. It needs to be a constant.

Size

Size is the count of elements in array.

It's accessed via the sizeof function.

int arr[] = { 1, 5, 6 }; cout << sizeof(arr) / sizeof(arr[0]);

Output:

3

Accessing values

Array's values are accessed via indexes starting from 0.

If we declare the following array:

int scores[4] = { 60, 78, 95, 88 };

It's elements are:

So if we type the following line:

cout << scores[0] << " " << scores[1];

It will print:

60 78

Index out of Bounds

Accessing index outside of the array results in unexpected behaviour.

Let's have an array with 4 elements. If we access the 4th or higher index, the behaviour of the program is uncertain.

Such example is:

int scores[4] = { 60, 78, 95, 88 }; cout << scores[4];

Printing All Elements

Let's have an example in which all elements of array are printed.

#include <iostream> using namespace std; int main() { const int size = 4; int scores[size] = { 60, 78, 95, 88 }; for (int i = 0; i < size; i++) { cout << scores[i] << " "; } }

Output:

60 78 95 88

For loop is a convenient way to access all elements since it can provide numbers from 0 to array's count.

Accessing empty element

If not specified, elements hold default values.

It depends on their type (int, string, double etc...).

The most common default value is 0 for numeric types or "" for strings.

The following example prints element with set and unset value:

#include <iostream> using namespace std; int main() { int ages[2] = {20}; cout << ages[0] << " " << ages[1]; }

Output:

20 0

Inserting Elements

Elements can be inserted by specifying index and value.

Let's have a program which fills array with values:

#include <iostream> using namespace std; int main() { int ages[3]; ages[0] = 15; ages[1] = 25; ages[2] = 28; }

Wrong type insertion

If we define an integer array but try to insert other type of value (like string), it will result in exception:

Such example is:

int ages[2]; ages[0] = 20; ages[1] = "Smith"; // causes exception

Calculating Average

To do that we need to find the sum of all elements and divide it to their count:

#include <iostream> using namespace std; int main() { const int count = 4; double prices[count] = {15, 20, 30, 45}; // Calculate Sum: double sum = 0; for (int i = 0; i < count; i++) { sum += prices[i]; } // Print Average: cout << sum / count; }

Output:

27.5