C# program where size of array index and elements are from user input and then search for a specific element

Question

I'm trying to create a program where the size of array index and its elements are from user input. And then the program will prompt the user to search for a specific element and will display where it is.

I've already come up with a code:

using System;

namespace ConsoleApplication1
{

class Program
{

  public static void Main(String [] args)
  {
    int a;
    Console.WriteLine("Enter size of index:");
    a= int.Parse(Console.ReadLine());
    int [] index = new int [a];
    for (int i=0; i<index.Length;i++)
    {
      Console.WriteLine("Enter number:");
      index[i]=int.Parse(Console.ReadLine());
    }

  }
}
}

The problem with this is that I can't display the numbers entered and I don't have any idea how to search for an array element. I'm thinking of using if statement.

Another thing, after entering the elements the program should display the numbers like Number 0 : 1

Is this correct: Console.WriteLine("Number"+index[a]+":"+index[i]);?

And where should I put the statement? after the for loop or within it?

Answer 1

You're on the right track. Look carefully at how you stuffed values into the array, and you might find a clue about "how to search for an array element" with specific value. This is a core introductory algorithm, so no shortcuts! You need to find the answer on your own :-).

Answer 2

What is the last line Console.WriteLine(index[i]);? It seems like you are using the loop variable outside the loop.

To display entered numbers (ie. if I understand well, the numbers in the array), you have just to walk through the array like this:

for (int i = 0; i < index.length; i++)
{
    Console.WriteLine(index[i]);
}

Since you want display numbers only after every number is entered, you may put this code only after finishing the loop where the user is entering the numbers:

// The user is entering the numbers (code copied from your question).
for (int i = 0; i < index.Length; i++)
{
    Console.WriteLine("Enter number: ");
    index[i] = int.Parse(Console.ReadLine());
}

// Now display the numbers entered.
for (int i = 0; i < index.length; i++)
{
    Console.WriteLine(index[i]);
}

// Finally, search for the element and display where it is.
int elementToSearchFor;
if (int.TryParse(Console.ReadLine(), out elementToSearchFor))
{
    // TODO: homework to do.
}

To search for a number, you can either walk through the array again and compare each element until finding a good one, or use Linq TakeWhile() method. (I suppose that your intent is not to use Linq, so I don't provide any further detail in this direction.)

Answer 3

You could use Array.IndexOf,