二叉树遍历

先序遍历：

1.       访问根结点

2.       按先序遍历左子树;

3.       按先序遍历右子树；

4.       例如：遍历已知二叉树结果为：A->B->D->G->H->C->E->F

中序遍历：

1.       按中序遍历左子树;

2.       访问根结点；

3.       按中序遍历右子树；

4.       例如遍历已知二叉树的结果：B->G->D->H->A->E->C->F

后序遍历：

1.       按后序遍历左子树；

2.       按后序遍历右子树；

3.       访问根结点；

4.       例如遍历已知二叉树的结果：G->H->D->B->E->F->C->A

层次遍历：

1.       从上到下，从左到右遍历二叉树的各个结点(实现时需要借辅助容器)；

2.       例如遍历已知二叉树的结果：A->B->C->D->E->F->G->H

using System;
using System.Collections.Generic;
using System.Text;

namespace structure
{
    class Program
    {
        二叉树结点数据结构的定义#region 二叉树结点数据结构的定义
        //二叉树结点数据结构包括数据域，左右结点以及父结点成员；
      class nodes<T>
        {
            T data;
            nodes<T> Lnode, Rnode, Pnode;
            public T Data
            {
                set { data = value; }
                get { return data; }

            }
            public nodes<T> LNode
            {
                set { Lnode = value; }
                get { return Lnode; }
            }
            public nodes<T> RNode
            {
                set { Rnode = value; }
                get { return Rnode; }

            }

            public nodes<T> PNode
            {
                set { Pnode = value; }
                get { return Pnode; }

            }
          public nodes()
          { }
          public nodes(T data)
          {
              this.data = data;
          }

        }
        #endregion

        先序编历二叉树#region 先序编历二叉树
        static void PreOrder<T>(nodes<T> rootNode)
        {
            if (rootNode != null)
            {
                Console.WriteLine(rootNode.Data);
                PreOrder<T>(rootNode.LNode);
                PreOrder<T>(rootNode.RNode);

            }
        }
       
        #endregion

        构造一棵已知的二叉树#region 构造一棵已知的二叉树

        static nodes<string> BinTree()
        {
            nodes<string>[] binTree = new nodes<string>[8];
            //创建结点
            binTree[0] = new nodes<string>("A");
            binTree[1] = new nodes<string>("B");
            binTree[2] = new nodes<string>("C");
            binTree[3] = new nodes<string>("D");
            binTree[4] = new nodes<string>("E");
            binTree[5] = new nodes<string>("F");
            binTree[6] = new nodes<string>("G");
            binTree[7] = new nodes<string>("H");
            //使用层次遍历二叉树的思想，构造一个已知的二叉树

            binTree[0].LNode = binTree[1];
            binTree[0].RNode = binTree[2];
            binTree[1].RNode = binTree[3];
            binTree[2].LNode = binTree[4];
            binTree[2].RNode = binTree[5];
            binTree[3].LNode = binTree[6];
            binTree[3].RNode = binTree[7];
            //返回二叉树的根结点
            return binTree[0];



        }
        #endregion

        中序遍历二叉树#region 中序遍历二叉树
        static void MidOrder<T>(nodes<T> rootNode)
        {
            if (rootNode != null)
            {
                MidOrder<T>(rootNode.LNode);
                Console.WriteLine(rootNode.Data);
                MidOrder<T>(rootNode.RNode);
            }
        }
        #endregion
        后序遍历二叉树#region 后序遍历二叉树
        static void AfterOrder<T>(nodes<T> rootNode)
        {
            if (rootNode != null)
            {
                AfterOrder<T>(rootNode.LNode);
                AfterOrder<T>(rootNode.RNode);
                Console.WriteLine(rootNode.Data);
            }

        }
        #endregion

        层次遍历二叉树#region 层次遍历二叉树
        static void LayerOrder<T>(nodes<T> rootNode)
        {
            nodes<T>[] Nodes = new nodes<T>[20];
            int front = -1;
            int rear = -1;
            if (rootNode != null)
            {
                rear++;
                Nodes[rear] = rootNode;

            }

            while (front != rear)
            {
                front++;
                rootNode = Nodes[front];
                Console.WriteLine(rootNode.Data);
                if (rootNode.LNode != null)
                {
                    rear++;
                    Nodes[rear] = rootNode.LNode;
                }
                if (rootNode.RNode != null)
                {
                    rear++;
                    Nodes[rear] = rootNode.RNode;
                }
            }
        }
       
        #endregion

        测试的主方法#region 测试的主方法
        static void Main(string[] args)
        {
            nodes<string> rootNode = BinTree();

            Console.WriteLine("先序遍历方法遍历二叉树：");
            PreOrder<string>(rootNode);
          
            Console.WriteLine("中序遍历方法遍历二叉树：");
            MidOrder<string>(rootNode);
           
            Console.WriteLine("后序遍历方法遍历二叉树：");
            AfterOrder<string>(rootNode);


            Console.WriteLine("层次遍历方法遍历二叉树：");
            LayerOrder<string>(rootNode);


            Console.Read();

        }
        #endregion
    }
}