What is wrong with this linear search?

Question

Basically I am working on my assignment and i need to make my code read a number then check to see if the number is in an array I created. This is the code at the moment starting from where i create the array
Console.WriteLine("Press enter to see question 7");
            Console.ReadKey();
            int MaxValue;
            int RandomNumber;
            Random MyRandom;
            MaxValue = 20;
            MyRandom = new Random();
            RandomNumber = MyRandom.Next(MaxValue);

            int[] firstArray = new int[10];
            for (int i = 0; i < 10; i++)
            {
                RandomNumber = MyRandom.Next(MaxValue);
                firstArray[i] = RandomNumber;
            }
            for (int i = 0; i < 10; i++)
            {
                Console.WriteLine("Item {0} in the array is {1}", i, firstArray[i]);
            }
            //8
            Console.WriteLine("Press enter to see question 8");
            Console.ReadKey();
            Console.WriteLine("The lowest number in the array is {0}", firstArray.Min());
            //9
            int j;
            for (j = 0; j < 20; j++)
            {
                if (linear_search(j, 7, firstArray))
                    System.Console.WriteLine(j + "if found in the array");
                else
                    System.Console.WriteLine(j + "is not found in the array");
            }
The problem I have at the moment is it says "the name "linear_search" does not exist in the current context". Also I know there are probably problems with the code anyway, since i'm not really sure how to use linear searches and can't find anywhere that explains it properly. I know the code at the moment isn't asking for input, and is just looking for 7 in the code, but that's just for while i make it work.

Vulpes · Answer

A linear search simply means that you look through a collection (such as an array) until you find the item that you're looking for. If the item is found you can return its index in the collection. If it's not found you can return some special number (-1 is usually used as indices start at 0) to the calling code. Most of your program is fine. I've filled in some code for the linear_search method and also added a few lines to obtain the number to search for in the array: using System; using System.Linq; class Test { static void Main() { Console.WriteLine(Press enter to see question 7); Console.ReadKey(); int MaxValue; int RandomNumber; Random MyRandom; MaxValue = 20; MyRandom = new Random(); RandomNumber = MyRandom.Next(MaxValue); int[] firstArray = new int[10]; for (int i = 0; i { RandomNumber = MyRandom.Next(MaxValue); firstArray[i] = RandomNumber; } for (int i = 0; i { Console.WriteLine(Item {0} in the array is {1} i firstArray[i]); } //8 Console.WriteLine(Press enter to see question 8); Console.ReadKey(); Console.WriteLine(The lowest number in the array is {0} firstArray.Min()); //9 Console.WriteLine(Press enter to see question 9); Console.ReadKey(); int j; Console.Write(Enter number to search for : ); j = int.Parse(Console.ReadLine()); int index = linear_search(j firstArray); if (index > 0) { Console.WriteLine({0} is found at index {1} in the array j index); } else { Console.WriteLine({0} is not found in the array j); } Console.WriteLine(Press any key to end program); Console.ReadKey(); } static int linear_search(int search int[] arr) { int index = -1; for(int i = 0; i { if(arr[i] == search) { index = i; break; } } return index; } }

Vulpes · Answer

There is a method called Array.IndexOf in the .NET Framework which does a linear search of an array but if you're learning C# you'll probably be expected to code it yourself rather than using built-in methods.

Jamie Dalley · Answer

Thanks a lot works fine now :) I thought linear_search was built in or something didn't realise it needed a method so that was probably what was confusing me.