数据结构——17 二叉树（递归）

Posted 2022-11-28 langtaol

二叉树——递归法

二叉树——使用递归方法，创建树、前中后序遍历树
建立树时，按照左子树小于树根，右子树大于树根，这样中序遍历就是有序表

#include<iostream>
using namespace std;
class node            //树节点定义

public:
	int data;         //元素值
	node *parent;     //父节点
	node *left;       //左子节点
	node *right;      //右子节点
public:
//	node():data(-1),parent(NULL),left(NULL),right(NULL);
	node(int num):data(num),parent(NULL),left(NULL),right(NULL);        //构造函数，初始化类成员变量


;

class tree            //树定义

public:
	tree(int num[],int len);           //构造函数


	void insertNode(int data);         //安左低右高插入树的节点
	void preOrderTree();               //前序
	void inOrderTree();                //中序             
	void postOrderTree();              //后序


private:
	void insertNode(node *root,int data);	    //插入递归
	void preOrderTree(node *current);           //前序递归
	void inOrderTree(node *current);            //中序递归
	void postOrderTree(node *current);          //后序递归


	node *root;                       //树的根节点

;

tree::tree(int num[],int len)         //构造函数

	root=new node(num[0]);
	for(int i=1;i<len;i++)
		insertNode(num[i]);           //调用插入函数


void tree::insertNode(int data)

	if(root!=NULL)
		insertNode(root,data); 


void tree::insertNode(node *current,int data)      //递归插入函数树节点函数

	if(data<= current->data)
	
		if(current->left==NULL)
		
			current->left =new node(data);
			current->left->parent=current;
		
		else 
			insertNode(current->left,data);
	


	else if(data> current->data)
	
		if(current->right==NULL)
		
			current->right =new node(data);
			current->right->parent=current;
		
		else 
			insertNode(current->right,data);
	


	return;


void tree::preOrderTree()      //前序遍历

	if(root==NULL)
		return;
	preOrderTree(root);

void tree::preOrderTree(node *current)

	if(current!=NULL)
	
		cout<<current->data<<"  ";
		preOrderTree(current->left);
		preOrderTree(current->right);
	


void tree::inOrderTree()       //中序遍历

	if(root==NULL)
		return;
	inOrderTree(root);

void tree::inOrderTree(node *current)

	if(current!=NULL)
	
		inOrderTree(current->left);
		cout<<current->data<<"  ";
		inOrderTree(current->right);
	





void tree::postOrderTree()     //后序遍历

	if(root==NULL)
		return;
	postOrderTree(root);

void tree::postOrderTree(node *current)

	if(current!=NULL)
	
	
		postOrderTree(current->left);
		postOrderTree(current->right);
		cout<<current->data<<"  ";
	



int main()

	int num[8]=5,3,7,2,4,6,8,1;
	tree t(num,8);


	cout<<"前序遍历:  ";
	t.preOrderTree();
	cout<<endl<<endl;


	cout<<"中序遍历:  ";
	t.inOrderTree();
	cout<<endl<<endl;


	cout<<"后序遍历:  ";
	t.postOrderTree();
	cout<<endl;


	return 0;

前面为了安全，程序写的比较麻烦，递归方法都放在private里，然后通过public里的接口调用，现在可以直接写成public的，容易理解。

#include<iostream>
using namespace std;
class node            //树节点定义

public:
	int data;         //元素值
	node *left;       //左子节点
	node *right;      //右子节点
public:
//	node():data(-1),parent(NULL),left(NULL),right(NULL);
	node(int num):data(num),left(NULL),right(NULL);        //构造函数，初始化类成员变量

;

class tree            //树定义

public:
	node *root;                       //树的根节点
	tree(int num[],int len);           //构造函数

	void insertNode(node *root,int data);	    //插入递归 按左低右高插入树的节点   
	void preOrderTree(node *current);           //前序递归
	void inOrderTree(node *current);            //中序递归
	void postOrderTree(node *current);          //后序递归
;

tree::tree(int num[],int len)         //构造函数

	root=new node(num[0]);
	for(int i=1;i<len;i++)
		insertNode(root,num[i]);      //调用插入函数


void tree::insertNode(node *current,int data)      //递归插入函数树节点函数

	if(data<= current->data)
	
		if(current->left==NULL)
			current->left =new node(data);
		else 
			insertNode(current->left,data);
	


	else
	
		if(current->right==NULL)
			current->right =new node(data);
		else 
			insertNode(current->right,data);
	
	



void tree::preOrderTree(node *current)    //前序遍历

	if(current!=NULL)
	
		cout<<current->data<<"  ";
		preOrderTree(current->left);
		preOrderTree(current->right);
	



void tree::inOrderTree(node *current)    //中序遍历

	if(current!=NULL)
	
		inOrderTree(current->left);
		cout<<current->data<<"  ";
		inOrderTree(current->right);
	



void tree::postOrderTree(node *current)   //后序遍历

	if(current!=NULL)
	
	
		postOrderTree(current->left);
		postOrderTree(current->right);
		cout<<current->data<<"  ";
	



int main()

	int num[8]=5,3,7,2,4,6,8,1;
	tree t(num,8);


	cout<<"前序遍历:  ";
	t.preOrderTree(t.root);
	cout<<endl<<endl;


	cout<<"中序遍历:  ";
	t.inOrderTree(t.root);
	cout<<endl<<endl;


	cout<<"后序遍历:  ";
	t.postOrderTree(t.root);
	cout<<endl;


	return 0;