二叉树遍历

很久没研究算法了，都陌生得很了，现在工作了，觉得要提高自己的水平，光是完成工作，学习新的知识是不够的，要多研究算法，要多磨练自己的思维能力逻辑能力，多做题，不能让自己的脑袋生锈……

 

从今天开始，坚持写写一些算法的C#实现，先从二叉树的遍历开始：

 

 

  1 //======================================================================
  2 //
  3 //        copyright (C) 2010 All rights reserved
  4 //        framework   : 3.5   
  5 //        filename    : Program
  6 //        description :
  7 //        author      : marvin(马非马)
  8 //        company     : Sysu.im.06imis
  9 //        create time : 2010-8-10 19:01:14
 10 //
 11 //======================================================================
 12 using System;
 13 using System.Collections.Generic;
 14 using System.Linq;
 15 using System.Text;
 16 
 17 namespace AlgorithmTest
 18 {
 19     class Program
 20     {
 21         static void Main(string[] args)
 22         {
 23             //Hanoi h = new Hanoi();
 24             //h.HanoiMove(5);
 25 
 26             First(CreateBinaryTree());
 27             Console.WriteLine("=====================");
 28             Middle(CreateBinaryTree());
 29             Console.WriteLine("=====================");
 30             After(CreateBinaryTree());
 31             Console.WriteLine("=====================");
 32             Layer(CreateBinaryTree());
 33         }
 34 
 35         /// <summary>
 36         /// 构建一棵二叉树
 37         /// </summary>
 38         /// <typeparam name="T"></typeparam>
 39         class BTreeNode<T>
 40         {
 41             T data;
 42             BTreeNode<T> lChild, rChild, parent;
 43 
 44             public T Data
 45             {
 46                 get { return data; }
 47                 set { data = value; }
 48             }
 49 
 50             public BTreeNode<T> LChild
 51             {
 52                 get { return lChild; }
 53                 set { lChild = value; }
 54             }
 55 
 56             public BTreeNode<T> RChild
 57             {
 58                 get { return rChild; }
 59                 set { rChild = value; }
 60             }
 61 
 62             public BTreeNode<T> Parent
 63             {
 64                 get { return parent; }
 65                 set { parent = value; }
 66             }
 67 
 68             public BTreeNode() { }
 69 
 70             public BTreeNode(T data)
 71             {
 72                 this.data = data;
 73             }
 74         }
 75 
 76         /// <summary>
 77         /// 创建如下的二叉树
 78         ///         A
 79         ///        / \
 80         ///       B   C
 81         ///      / \  /\
 82         ///     D   EF  G
 83         ///    /
 84         ///   H
 85         /// </summary>
 86         /// <returns>返回根节点</returns>
 87         static BTreeNode<string> CreateBinaryTree()
 88         {
 89             BTreeNode<string>[] nodes = new BTreeNode<string>[8];
 90 
 91             nodes[0] = new BTreeNode<string>("A");
 92             nodes[1] = new BTreeNode<string>("B");
 93             nodes[2] = new BTreeNode<string>("C");
 94             nodes[3] = new BTreeNode<string>("D");
 95             nodes[4] = new BTreeNode<string>("E");
 96             nodes[5] = new BTreeNode<string>("F");
 97             nodes[6] = new BTreeNode<string>("G");
 98             nodes[7] = new BTreeNode<string>("H");
 99 
100             nodes[0].LChild = nodes[1];
101             nodes[0].RChild = nodes[2];
102 
103             nodes[1].LChild = nodes[3];
104             nodes[1].RChild = nodes[4];
105 
106             nodes[2].LChild = nodes[5];
107             nodes[2].RChild = nodes[6];
108 
109             nodes[3].LChild = nodes[7];
110 
111             return nodes[0];
112         }
113 
114         /// <summary>
115         /// 先（根）序遍历
116         /// </summary>
117         /// <param name="node">根节点</param>
118         static void First(BTreeNode<string> node)
119         {
120             Console.WriteLine(node.Data);
121             if (node.LChild != null)
122             {
123                 First(node.LChild);
124             }
125             if (node.RChild != null)
126             {
127                 First(node.RChild);
128             }
129         }
130 
131         /// <summary>
132         /// 中（根）序遍历
133         /// </summary>
134         /// <param name="node">根节点</param>
135         static void Middle(BTreeNode<string> node)
136         {
137             if (node.LChild != null)
138                 Middle(node.LChild);
139             Console.WriteLine(node.Data);
140             if (node.RChild != null)
141                 Middle(node.RChild);
142         }
143 
144         /// <summary>
145         /// 后（根）序遍历
146         /// </summary>
147         /// <param name="node">根节点</param>
148         static void After(BTreeNode<string> node)
149         {
150             if (node.LChild != null)
151                 After(node.LChild);
152             if (node.RChild != null)
153                 After(node.RChild);
154             Console.WriteLine(node.Data);
155         }
156 
157         /// <summary>
158         /// 层次遍历
159         /// </summary>
160         /// <param name="rootNode">根节点</param>
161         static void Layer(BTreeNode<string> rootNode)
162         {
163             int front = -1;
164             int rear = -1;
165             BTreeNode<string>[] nodes = new BTreeNode<string>[20];
166 
167             if (rootNode != null)
168             {
169                 rear++;
170                 nodes[rear] = rootNode;
171             }
172 
173             while (front != rear)
174             {
175                 front++;
176                 // 逐层把左右几点添加进来
177                 rootNode = nodes[front];
178                 Console.WriteLine(rootNode.Data);
179 
180                 if (rootNode.LChild != null)
181                 {
182                     rear++;
183                     nodes[rear] = rootNode.LChild;
184                 }
185                 if (rootNode.RChild != null)
186                 {
187                     rear++;
188                     nodes[rear] = rootNode.RChild;
189                 }
190             }
191         }
192     }
193 }
194