Leet code tree questions

Implementation using C#

Author: jianminchen

TreeDemo.cs

@@ -0,0 +1,200 @@
+using System;
+using System.Collections;
+using System.Collections.Generic;
+using System.Linq;
+using System.Text;
+using System.Threading.Tasks;
+
+/*  May 26, 2015 http://arachnode.net/blogs/programming_challenges/archive/2009/09/25/recursive-tree-traversal-orders.aspx   */
+namespace TreeTraversal
+{
+    internal class Program
+    {
+        private static readonly Queue<Node> Queue = new Queue<Node>();
+
+        private static readonly Queue<Node> Queue2 = new Queue<Node>();
+
+        private static void Main()
+        {
+            var node1 = new Node();
+            var node2 = new Node();
+            var node3 = new Node();
+            var node4 = new Node();
+            var node5 = new Node();
+            var node6 = new Node();
+            var node7 = new Node();
+
+            node1.Value = 1;
+            node2.Value = 2;
+            node3.Value = 3;
+            node4.Value = 4;
+            node5.Value = 5;
+            node6.Value = 6;
+            node7.Value = 7;
+
+            node1.Left = node2;
+            node1.Right = node3;
+
+            node2.Left = node4;
+            node2.Right = node5;
+
+            node3.Left = node6;
+            node3.Right = node7;
+
+            Console.WriteLine("PreorderTraversal");
+
+            PreorderTraversal(node1);
+
+            Console.WriteLine("PreorderTraversalIterative");
+            ArrayList list = preorderTraversalIterative(node1);
+            foreach (Object s in list)
+            {
+                int tmp = (int)s;
+                Console.WriteLine(tmp); 
+            }
+
+            Console.WriteLine("InorderTraversal");
+
+            InorderTraversal(node1);
+
+            Console.WriteLine("PostorderTraversal");
+
+            PostorderTraversal(node1);
+
+            Console.WriteLine("BreathFirstTraversal");
+
+            BreadthFirstTraversal(node1);
+
+            Console.WriteLine("BreathFirstTraversalIterative");
+
+            BreadthFirstTraversalIterative(node1);
+
+            Console.ReadLine();
+
+
+        }
+
+        private static void PreorderTraversal(Node node)
+        {
+            if (node == null)
+            {
+                return;
+            }
+
+            Console.WriteLine(node.Value.ToString());
+
+            PreorderTraversal(node.Left);
+            PreorderTraversal(node.Right);
+        }
+
+        private static void InorderTraversal(Node node)
+        {
+            if (node == null)
+            {
+                return;
+            }
+
+            InorderTraversal(node.Left);
+
+            Console.WriteLine(node.Value);
+
+            InorderTraversal(node.Right);
+        }
+
+        private static void PostorderTraversal(Node node)
+        {
+            if (node == null)
+            {
+                return;
+            }
+
+            PostorderTraversal(node.Left);
+
+            PostorderTraversal(node.Right);
+
+            Console.WriteLine(node.Value);
+        }
+
+        private static void BreadthFirstTraversal(Node node)
+        {
+            if (node == null)
+            {
+                return;
+            }
+
+            Queue.Enqueue(node.Left);
+
+            Queue.Enqueue(node.Right);
+
+            Console.WriteLine(node.Value);
+
+            if (Queue.Count != 0)
+            {
+                BreadthFirstTraversal(Queue.Dequeue());
+            }
+        }
+
+        private static void BreadthFirstTraversalIterative(Node node)
+        {
+            if (node == null)
+            {
+                return;
+            }
+
+            Queue2.Enqueue(node);             
+
+            while (Queue2.Count != 0)
+            {
+                //BreadthFirstTraversal(Queue.Dequeue());
+                Node tmpNode = Queue2.Dequeue();
+
+                // visit the node
+                Console.WriteLine(tmpNode.Value);
+
+                Node left = tmpNode.Left;
+                Node right = tmpNode.Right;
+
+                if (left != null)
+                    Queue2.Enqueue(left);
+
+                if (right != null)
+                    Queue2.Enqueue(right);
+            }
+        }
+
+
+        private static ArrayList preorderTraversalIterative(Node root) {
+            ArrayList result = new ArrayList();
+            Node p = new Node();
+
+            Stack s = new Stack();
+
+            p = root;
+            if (p != null) s.Push(p);
+
+            while (s.Count > 0) {
+                p = (Node)s.Peek();
+
+                s.Pop();
+
+                result.Add(p.Value);
+
+                if (p.Right != null) s.Push(p.Right);
+                if (p.Left != null) s.Push(p.Left);
+            }
+
+            return result;
+        }
+    }
+
+    internal class Node
+    {
+        public int Value { get; set; }
+        public Node Left { get; set; }
+        public Node Right { get; set; }
+        public override string ToString()
+        {
+            return Value.ToString();
+        }
+    }
+}