TreeNode sample from the PPP book by Robert C. Martin

gistfile1.cs

using System;
public class TreeMap
{
    private TreeMapNode topNode = null;

    public void Add(IComparable key, object value)
    {
        if (topNode == null)
            topNode = new TreeMapNode(key, value);
        else
            topNode.Add(key, value);
    }

    public object Get(IComparable key)
    {
        return topNode == null ? null : topNode.Find(key);
    }

    internal class TreeMapNode
    {
        private static readonly int LESS = 0;
        private static readonly int GREATER = 1;
        private IComparable key;
        private object value;

        private TreeMapNode[] nodes = new TreeMapNode[2];

        public TreeMapNode(IComparable key, object value)
        {
            this.key = key;
            this.value = value;
        }

        public object Find(IComparable key)
        {
            if (key.CompareTo(this.key) == 0) return value;
            return FindSubNodeForKey(SelectSubNode(key), key);
        }

        private int SelectSubNode(IComparable key)
        {
            return (key.CompareTo(this.key) < 0) ? LESS : GREATER;
        }

        private object FindSubNodeForKey(int node, IComparable key)
        {
            return nodes[node] == null ? null : nodes[node].Find(key);
        }

        public void Add(IComparable key, object value)
        {
            if (key.CompareTo(this.key) == 0)
                this.value = value;
            else
                AddSubNode(SelectSubNode(key), key, value);
        }

        private void AddSubNode(int node, IComparable key, object value)
        {
            if (nodes[node] == null)
                nodes[node] = new TreeMapNode(key, value);
            else
                nodes[node].Add(key, value);
        }
    }
}