Arrays

An array is a collection of similar types of data. For example:

Suppose we need to record the age of 5 students. Instead of creating 5 separate variables, we can simply create an array:

Elements of an array

Array Declaration

datatype[] arrayName;

Here,

dataType - data type like int, string, char, etc.

arrayName - it is an identifier

Let's see an example,

// declare an array
int[] age;

// allocate memory for array
age = new int[5];

Here, we have created an array named age. It can store 5 elements of int type.

Array initialization

In C#, we can initialize an array during the declaration. For example:

 int [] numbers = {1, 2, 3, 4, 5}; 

Here, we have created an array named numbers and initialized it with values 1, 2, 3, 4, and 5 inside the curly braces

Note that we have not provided the size of the array. In this case, the C# automatically specifies the size by counting the number of elements!

Array indexing

We can use the index number to initialize an array in C#. For example:

// declare an array
int[] age = new int[5];

//initializing array
age[0] = 12;
age[1] = 4;
age[2] = 5;
...

Array indexing

As you can see from the above diagram, An array index always starts at 0.

The first element of an array is at index 0. If the size of an array is 5, the index of the last element will be at 4

Access Array Elements

We can access the elements in the array using the index of the array. For example:

// access element at index 2
array[2];

// access element at index 4
array[4];

Exercise

Complete the code to get the expected output

Expected Output:

Element in first index : 1
Element in second index : 2
Element in third index : 3

using System;

class Program  {
    static void Main() {

      // todo - create an array called numbers with elements 1, 2 and 3 in it

      //access first element
      Console.WriteLine("Element in first index : " + /*todo*/); 

      //access second element
      Console.WriteLine("Element in second index : " + /*todo*/);

      //access third element
      Console.WriteLine("Element in third index : " + /*todo*/);

      Console.ReadLine();

    }
}

Iterating array using for loop

In C#, we can use loops to iterate through each element of an array. For example:

class Program {
    static void Main(string[] args) {

      int[] numbers = { 1, 2, 3};
 	 
      for(int i=0; i < numbers.Length; i++) {
        Console.WriteLine("Element in index " + i + ": " + numbers[i]);
      }

      Console.ReadLine();
    }
  }

Output:

Element in index 0: 1
Element in index 1: 2
Element in index 2: 3

Here, the Length property of the array gives the size of the array.

Iterating array using foreach loop

We can also use a foreach loop to iterate through the elements of an array. For example:

class Program {
    static void Main(string[] args) {
      int[] numbers = {1, 2, 3};

      Console.WriteLine("Array Elements: ");

      foreach(int num in numbers) {
        Console.WriteLine(num);
      }

      Console.ReadLine();
    }
  }

Output

Array Elements:
1
2
3

Exercise

Find the sum and average of 5 numbers given by user:

Expected output:

Enter Number 1
1
Enter Number 2
2
Enter Number 3
3
Enter Number 4
4
Enter Number 5
5
Given numbers are:
1 2 3 4 5 
Sum is 15 and Avg is 3

using System;

class Program  {
    static void Main(string[] args) {
        int[] nums = /*todo*/
        
        for(/*todo*/){
            Console.WriteLine("Enter Number {0}", i+1);
            /*todo*/
        }   

        int sum =0;
        foreach(/*todo*/)   
            sum+=num;
        
        int avg = /*todo*/

        Console.WriteLine("Given numbers are:");
        foreach(/*todo*/)   
            Console.Write($"{num} ");

        Console.WriteLine();
        Console.WriteLine($"Sum is {/*todo*/} and Avg is {/*todo*/}");
    }
}

Exercise

Find the largest word among the words entered by user

Expected Output

How many words do you want to input?
3
Enter word no 1
computer
Enter word no 2
is
Enter word no 3
fun
Among the given words, largest word is computer

using System;

class Program  {
    static void Main() {
       Console.WriteLine("How many words do you want to input?");
       int size = Convert.ToInt32(Console.ReadLine());

       /*todo - declare words array*/
       for(/*todo*/){
           Console.WriteLine($"Enter word no {i+1}");
          /*todo - store the words*/
       }

       int large =0;
       string largestWord = string.Empty;
       foreach(/*todo*/){
           if(word.Length > large){
               large = word.Length;
               largestWord = word;
           }           
       }
       Console.WriteLine($"Among the given words, largest word is {/*todo*/}");
    }
}