Reverse Method for an Array of int

Question

I have this as Main

int[] M ={ 10, 2, 30, 4, 50, 6, 7, 80 };

MyMath.Reverse(M);

for (int i = 0; i < M.Length; i++)

    Console.WriteLine(M[i].ToString() + ", ");

---

After I created the class MyMath I made the Reverse method

public int Reverse(Array M)
 {
     int len = M.Length;
       for (int i = 0; i < len / 2; i++) 
       {
           int temp = M[i]; M[i] = M[len - i - 1]; M[len - i - 1] = temp;

       }           
 }

but I'm sure it's wrong because it's not working :-) so do you have a different code to write in the reverse method?

note: I don't want to use the built in Reverse in the Array class

---

yes guys when i used the built in reverse method i got this error

Process is terminated due to StackOverflowException.

thats after i wrote the method as

public static int Reverse(Array M)
{
    return Reverse(M);
}

So then I tried to create my own reverse method and there i got stuck

Answer 1

You need to pass you array as a reference. In C#, you do that by using the keyword 'ref' when declaring your parameters.

What you are currently doing is basically reversing a copy of your array which is never passed back to the caller.

Answer 2

It makes next to no sense to not use Array.Reverse. But if you really want to do it, ONE option could be to duplicate the array into a Stack, although I do not believe that this is very fast (but I have not profiled it either):

private void Whatever()
{
    int[] M = { 10, 2, 30, 4, 50, 6, 7, 80 };
    ReverseArray(ref M);

}

private void ReverseArray(ref int[] input)
{
    Stack<int> tmp = new Stack<int>();
    foreach (int i in input)
    {
        tmp.Push(i);
    }
    input = tmp.ToArray();
}

Answer 3

It would be very helpful if you elaborated "Does not work". Code can not work in a bazillion and two ways. Does it not compile, does it give wrong results (in this case, show us the test input, the actual output and the expectd output), does it explode or does it make demons fly out of your nose?

Furhermore, from what I see from here, you will have fun with arrays with odd length [Edit or not?]

Answer 4

To fix your problem, change your method to:

// the built-in returns void, so that needed to be changed...
public static void Reverse(Array M)
{
    Array.Reverse(M); // you forgot to reference the Array class in yours
}

There, no Stack Overflow problems.

Answer 5

Working from your

public static int Reverse(Array M)
{
    return Reverse(M);
}

You have 2 problems.

1. Reverse(M) looks like the same function that you're in, so you're calling your new function, which calls itself, which calls itself, etc., resulting in the stack overflow. Change to return Array.Reverse(M);
2. Array.Reverse returns a void, so if you need to return an int (not sure what it's supposed to be here) you'll need to supply your own. Or change your Reverse function to be void.