0025二叉树的设计与实现

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按先根次序遍历二叉树，利用递归算法。算法基本描述：

1）二叉树为空，返回；否则继续；

2）从根节点开始，访问当前节点；

3）按先根次序遍历当前节点左子树；

3）按先根次序遍历当前节点右子树；

先定义二叉树节点类：

#ifndef TreeNode1_H_#define TreeNode1_H_#include <iostream>using namespace  std;class TreeNode1{public:char data;TreeNode1 *left,*right;TreeNode1(char ch='?');~TreeNode1(){}void preorderChild(TreeNode1 *p);void inorderChild(TreeNode1 *p);void postorderChild(TreeNode1 *p);};TreeNode1::TreeNode1(char ch){data = ch;left = NULL;right = NULL;}//preorder void TreeNode1::preorderChild(TreeNode1 *p){if (p!=NULL){cout<<p->data<<" ";preorderChild(p->left);preorderChild(p->right);}}//inordervoid TreeNode1::inorderChild(TreeNode1 *p){if (p!=NULL){inorderChild(p->left);cout<<p->data<<" ";inorderChild(p->right);}}//postordervoid TreeNode1::postorderChild(TreeNode1 *p){if (p!=NULL){postorderChild(p->left);postorderChild(p->right);cout<<p->data<<" ";}}#endif//TreeNode1_H_

再定义二叉树类：

#ifndef Tree1_H_#define Tree1_H_#include "TreeNode1.h"#include <iostream>using namespace std;class Tree1{public:TreeNode1 *root;Tree1(char *str="");~Tree1();TreeNode1* create(char *str);void destroy(TreeNode1 *p);//destroy binary treevoid preorder();void inorder();void postorder();};void Tree1::preorder(){cout<<"先序遍历二叉树：";root->preorderChild(root);cout<<endl;}void Tree1::inorder(){cout<<"中序遍历二叉树：";root->inorderChild(root);cout<<endl;}void Tree1::postorder(){cout<<"后序遍历二叉树：";root->postorderChild(root);cout<<endl;}//以标明空子树的先序次序遍历建立二叉树Tree1::Tree1(char *str){root=NULL;if (str!=""){cout<<"创建二叉树："<<endl;root=create(str);cout<<endl;}}TreeNode1 *Tree1::create(char *str){TreeNode1 *p=NULL;static int i=0;cout<<"调用"<<str[i]<<endl;if(str[i]!='.')//空子树标记一个点{p=new TreeNode1(str[i]);i++;p->left=create(str);p->right=create(str);}elsei++;if(p==NULL)cout<<"返回NULL"<<endl;elsecout<<"返回"<<p->data<<endl;return p;}//撤销二叉树Tree1::~Tree1(){cout<<"撤销二叉树：";destroy(root);root=NULL;cout<<endl;}void Tree1::destroy(TreeNode1 *p){if(p!=NULL){destroy(p->left);destroy(p->right);cout<<p->data<<" ";delete p;}}#endif//Tree_H_

在主函数文件中检测：

#include "Tree1.h"void main(void){char *str="ABD.G...CE..FH...";cout<<"the Tree: "<<str<<endl;Tree1 t(str);t.preorder();t.inorder();t.postorder();}

结果：

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