使用c++ 生成一颗简单的二叉树

二叉树的生成方式有千千万万种，下面介绍使用c++来实现简单的二叉树的方法，通过链表的结构来生成。

二叉树是由若干个节点组成，所以我们先要声明一个节点的类；头文件和函数实现方法分开；

//
//  node.h
//  data_structer
//
//  Created by 张钊 on 2020/3/2.
//  Copyright © 2020 张钊. All rights reserved.
//

#ifndef node_h
#define node_h
#include<iostream>
#include<cmath>
using namespace std;

class Node;
typedef void (*Visit)(const Node *node);
class Node
{
public:
    int nodeValue;
    Node *l_child;
    Node *r_child;
    
public:
    Node(int value = 0);
    ~Node();
    
public:
    int degree() const;
    int depth() const;
    int count() const;
    
public:
    void preOrder(Visit visit) const;
    void midOrder(Visit visit) const;
    void postOrder(Visit visit) const;
};

#endif /* node_h */

//  node.cpp
//  data_structer
//
//  Created by 张钊 on 2020/3/8.
//  Copyright © 2020 张钊. All rights reserved.
//

#include "node.h"

Node::Node(int value):nodeValue(value)
{
    l_child = NULL;
    r_child = NULL;
}

Node::~Node()
{
    if(l_child != NULL)
    {
        delete l_child;
    }
    if(r_child != NULL)
    {
        delete r_child;
    }
}

int Node::degree() const
{
    if(l_child == NULL && r_child == NULL)
    {
        return 0;
    }
    if(l_child != NULL && r_child != NULL)
    {
        return 2;
    }
    return 1;
}

int Node::depth() const
{
    int l_depth = 0;
    int r_depth = 0;
    if(l_child != NULL)
    {
        l_depth += l_child->depth();
    }
    if(r_child != NULL)
    {
        r_depth += r_child->depth();
    }
    return max(l_depth, r_depth) + 1;
}

int Node::count() const
{
    int l_count = 0;
    int r_count = 0;
    if(l_child != NULL)
    {
        l_count += l_child->count();
    }
    if(r_child != NULL)
    {
        r_count += r_child->count();
    }
    return l_count + r_count + 1;
}

void Node::preOrder(Visit visit) const
{
    (*visit)(this);
    if(this->l_child != NULL)
    {
        this->l_child->preOrder(visit);
    }
    if(this->r_child != NULL)
    {
        this->r_child->preOrder(visit);
    }
}

void Node::midOrder(Visit visit) const
{
    if(this->l_child != NULL)
    {
        this->l_child->preOrder(visit);
    }
    (*visit)(this);
    if(this->r_child != NULL)
    {
        this->r_child->preOrder(visit);
    }
}

void Node::postOrder(Visit visit) const
{
    if(this->l_child != NULL)
    {
        this->l_child->preOrder(visit);
    }
    if(this->r_child != NULL)
    {
        this->r_child->preOrder(visit);
    }
    (*visit)(this);
}

这样我们就实现了基本的节点的功能，下面开始进行二叉树的构建，这里创建二叉树利用map里面的key-》value，而map也是利用红黑树实现的。。

//  tree.h
//  data_structer
//
//  Created by 张钊 on 2020/3/2.
//  Copyright © 2020 张钊. All rights reserved.
//

#ifndef tree_h
#define tree_h
#include "node.h"
#include <map>
using namespace std;

class BinaryTree
{
private:
    Node *root;
    
private:
    Node *create(map<int, int> &tree, int index);
    
public:
    BinaryTree();
    BinaryTree(map<int, int> &tree);
    ~BinaryTree();
    
public:
    int depth() const;
    int count() const;
    
public:
    void preOrder(Visit visit) const;
    void midOrder(Visit visit) const;
    void postOrder(Visit visit) const;
};

#endif

//  tree.cpp
//  data_structer
//
//  Created by 张钊 on 2020/3/8.
//  Copyright © 2020 张钊. All rights reserved.
//

#include "tree.h"

BinaryTree::BinaryTree()
{
    root = NULL;
}

Node* BinaryTree::create(map<int, int> &tree, int index)
{
    if(tree.find(index) == tree.end())
    {
        return NULL;
    }
    Node *node = new Node();
    node->nodeValue = tree[index];
    node->l_child = create(tree, index * 2);
    node->r_child = create(tree, index * 2 + 1);
    return node;
}

BinaryTree::BinaryTree(map<int, int> &tree)
{
    root = create(tree, 1);
}

BinaryTree::~BinaryTree()
{
    if(root != NULL)
    {
        delete root;
    }
}

int BinaryTree::depth() const
{
    return root->depth();
}

int BinaryTree::count() const
{
    return root->count();
}

void BinaryTree::preOrder(Visit visit) const
{
    root->postOrder(visit);
    cout << endl;
}

void BinaryTree::midOrder(Visit visit) const
{
    root->midOrder(visit);
    cout << endl;
}

void BinaryTree::postOrder(Visit visit) const
{
    root->postOrder(visit);
    cout << endl;
}

最后进行简单的调试

//  main.cpp
//  data_structer
//
//  Created by 张钊 on 2020/3/2.
//  Copyright © 2020 张钊. All rights reserved.
//
#include "node.h"
#include "tree.h"
using namespace std;

void visit(const Node *node)
{
    cout << node->nodeValue << " ";
}

void test01()
{
    map<int, int> tree;
    for(int i = 1; i < 10; ++i)
    {
        tree[i] = i * i;
    }
    BinaryTree *binarytree = new BinaryTree(tree);
    cout << "the depth is " << binarytree->depth() << endl;
    cout << "the total number is " << binarytree->count() << endl;
    binarytree->postOrder(visit);
    binarytree->midOrder(visit);
    binarytree->postOrder(visit);
}

int main(int argc, const char * argv[]) {
    // insert code here...
    test01();
    return 0;
}

运行结果如下：

the depth is 4

the total number is 9

4 16 64 81 25 9 36 49 1 

4 16 64 81 25 1 9 36 49 

4 16 64 81 25 9 36 49 1 

Program ended with exit code: 0