C# Splitting An Array

Question

I need to split an array of indeterminate size, at the midpoint, into two separate arrays.

The array is generated from a list of strings using ToArray().

        public void AddToList ()
        {
            bool loop = true;
            string a = "";

            Console.WriteLine("Enter a string value and press enter to add it to the list");
            while (loop == true)
            {
                a = Console.ReadLine();

                if (a != "")
                {
                    mylist.Add(a);
                }
                else
                {
                    loop = false;
                }
            }

        }

        public void ReturnList()
        {
            string x = "";
            foreach (string number in mylist)
            {
                x = x + number + " ";
            }
            Console.WriteLine(x);
            Console.ReadLine();
        }

    }

    class SplitList
    {
        public string[] sTop;
        public string[] sBottom;

        public void Split(ref UList list)  
        {
            string[] s = list.mylist.ToArray();

            //split the array into top and bottom halfs

        }
    }

    static void Main(string[] args)
    {
        UList list = new UList();
        SplitList split = new SplitList();

        list.AddToList();
        list.ReturnList();

        split.Split(ref list);
    }
}

}

Answer 1

Why don't you allocate two arrays and copy the contents ?

EDIT: here you go:

        String[] origin = new String[4];
        origin[0] = "zero";
        origin[1] = "one";
        origin[2] = "two";
        origin[3] = "three";

        Int32 topSize = origin.Length / 2;
        Int32 bottomSize = origin.Length - topSize;
        String[] sTop = new String[topSize];
        String[] sBottom = new String[bottomSize];
        Array.Copy(origin, sTop, topSize);
        Array.Copy(origin, topSize , sBottom, 0, bottomSize);

Answer 2

You could use the following method to split an array into 2 separate arrays

public void Split<T>(T[] array, int index, out T[] first, out T[] second) {
  first = array.Take(index).ToArray();
  second = array.Skip(index).ToArray();
}

public void SplitMidPoint<T>(T[] array, out T[] first, out T[] second) {
  Split(array, array.Length / 2, out first, out second);
}

Answer 3

Use a generic split method:

public static void Split<T>(T[] source, int index, out T[] first, out T last)
{
    int len2 = source.Length - index;
    first = new T[index];
    last = new T[len2];
    Array.Copy(source, 0, first, 0, index);
    Array.Copy(source, index, last, 0, len2);
}

Answer 4

Why are you passing the UList as ref? There doesn't appear to be a need for that.

I would use a generic Split method if I needed to do this:

public void Split<T>(T[] array, out T[] left, out T[] right)
{
    left = new T[array.Length / 2];
    right = new T[array.Length - left.Length];

    Array.Copy(array, left, left.Length);
    Array.Copy(array, left.Length, right, 0, right.Length);
}

Answer 5

I think what you're looking for is the Array class, specifically the Array.Copy static method. You can think of that class as containing the methods that would be instance methods of arrays if C# arrays had methods.

Answer 6

If you don't have Linq, you can use Array.Copy:

public void Split(ref UList list)
{
    string[] s = list.mylist.ToArray();

    //split the array into top and bottom halfs
    string[] top = new string[s.Length / 2];
    string[] bottom = new string[s.Length - s.Length / 2];
    Array.Copy(s, top, top.Length);
    Array.Copy(s, top.Length, bottom, 0, bottom.Length);

    Console.WriteLine("Top: ");
    foreach (string item in top) Console.WriteLine(item);
    Console.WriteLine("Bottom: ");
    foreach (string item in bottom) Console.WriteLine(item);
}