二叉树遍历：先序、中序、后序和层次遍历

public class BinaryNode
    {
        public int Data;
        public BinaryNode Left;
        public BinaryNode Right;
    }


public class BinaryTree
    {
        public void PreOrder(BinaryNode node)
        {
            if (node != null)
            {
                Console.WriteLine(node.Data);

                PreOrder(node.Left);
                PreOrder(node.Right);
            }
        }

        public void MidOrder(BinaryNode node)
        {
            if (node != null)
            {
                MidOrder(node.Left);
                Console.WriteLine(node.Data);
                MidOrder(node.Right);
            }
        }

        public void AfterOrder(BinaryNode node)
        {
            if (node != null)
            {
                AfterOrder(node.Left);
                AfterOrder(node.Right);
                Console.WriteLine(node.Data);
            }
        }

        public void LayerOrder(BinaryNode node)
        {
            if (node != null)
            {
                CurrentLayer(node.Left);
                CurrentLayer(node.Right);

                LayerOrder(node.Left);
                LayerOrder(node.Right);
            }
        }

        private void CurrentLayer(BinaryNode node)
        {
            if (node != null)
            {
                Console.WriteLine(node.Data);
            }
        }

    }

测试：

            BinaryNode n1 = new BinaryNode();
            n1.Data = 27;

            BinaryNode n2 = new BinaryNode();
            n2.Data = 83;

            BinaryNode n3 = new BinaryNode();
            n3.Data = 123;

            BinaryNode n4 = new BinaryNode();
            n4.Data = 98;

            BinaryNode n5 = new BinaryNode();
            n5.Data = 94;

            BinaryNode n6 = new BinaryNode();
            n6.Data = 48;

            BinaryNode n7 = new BinaryNode();
            n7.Data = 61;

            n1.Left = n2;
            n1.Right = n3;
            n1.Left.Left = n4;
            n1.Left.Right = n5;
            n1.Right.Right = n6;
            n1.Right.Right.Left = n7;

            BinaryTree bTree = new BinaryTree();

            Console.WriteLine("Pre Order Binary Tree:");
            bTree.PreOrder(n1);

            Console.WriteLine("Midd Order Binary Tree:");
            bTree.MidOrder(n1);

            Console.WriteLine("After Order Binary Tree:");
            bTree.AfterOrder(n1);

            Console.WriteLine("Layer Order Binary Tree:");
            bTree.LayerOrder(n1);

            Console.ReadLine();