数据结构与算法（C语言版）__二叉树

二叉树的表示：
数组表示：
链表表示：

二叉树的遍历：
前序遍历
中序遍历
后序遍历
层序遍历
今天我们用链表实现二叉树。
在VS2013中新建项目，在头文件中加入 二叉树.h在源文件中加入main.cpp

//二叉树.h
#ifndef _二叉树_H
#define _二叉树_H
#include<queue>

using namespace std;
template<class T> class BinaryTree;

template<class T>
class TreeNode{
public:
    TreeNode(){
        leftChild = NULL;
        rightChild = NULL;
    }
    T data;
    TreeNode<T> *leftChild;
    TreeNode<T> *rightChild;
};

template<class T>
class BinaryTree{
public:
    //二叉树可以进行的操作
    void InOrder();
    void InOrder(TreeNode<T>* currentNode);
    void PreOrder();
    void PreOrder(TreeNode<T>* currentNode);
    void PostOrder();
    void PostOrder(TreeNode<T>* currentNode);
    void LevelOrder();
    void Visit(TreeNode<T>* currentNode);
    TreeNode<T> *root;
};

template<class T>
void BinaryTree<T>::LevelOrder(){
    std::queue<TreeNode<T>*> q;
    TreeNode<T>* currentNode = root;
    while (currentNode){
        Visit(currentNode);
        if (currentNode->leftChild) q.push(currentNode->leftChild);
        if (currentNode->rightChild) q.push(currentNode->rightChild);
        if (q.empty())return;
        currentNode = q.front();
        q.pop();
    }
}
template<class T>
void BinaryTree<T>::Visit(TreeNode<T>* currentNode){
    std::cout << currentNode->data;
}


template<class T>
void BinaryTree<T>::InOrder(){
    InOrder(root);
}

template<class T>
void BinaryTree<T>::InOrder(TreeNode<T>* currentNode){
    if (currentNode){
        InOrder(currentNode->leftChild);
        Visit(currentNode);
        InOrder(currentNode->rightChild);
    }
}

template<class T>
void BinaryTree<T>::PreOrder(){
    PreOrder(root);
}

template<class T>
void BinaryTree<T>::PreOrder(TreeNode<T>* currentNode){
    if (currentNode){
        Visit(currentNode);
        PreOrder(currentNode->leftChild);
        PreOrder(currentNode->rightChild);
    }
}

template<class T>
void BinaryTree<T>::PostOrder(){
    PostOrder(root);
}

template<class T>
void BinaryTree<T>::PostOrder(TreeNode<T>*currentNode){
    if (currentNode){
        PostOrder(currentNode->leftChild);
        PostOrder(currentNode->rightChild);
        Visit(currentNode);
    }
}
#endif

//main.cpp
#include<iostream>

#include"二叉树.h"

using namespace std;

int main(){

    cout << "测试二叉树：" << endl;

    BinaryTree<char> tree;
    TreeNode<char> 加, 减, 乘, 除, a, b, c, d, e;
    加.data = '+';
    减.data = '-';
    乘.data = '*';
    除.data = '/';
    a.data = 'A';
    b.data = 'B';
    c.data = 'C';
    d.data = 'D';
    e.data = 'E';

    tree.root = &加;
    加.leftChild = &减;
    加.rightChild = &e;
    减.leftChild = &乘;
    减.rightChild = &d;
    乘.leftChild = &除;
    乘.rightChild = &c;
    除.leftChild = &a;
    除.rightChild = &b;

    cout << "中序遍历：" << endl;
    tree.InOrder();
    cout << endl;

    cout << "前序遍历：" << endl;
    tree.PreOrder();
    cout << endl;

    cout << "后序遍历：" << endl;
    tree.PostOrder();
    cout << endl;

    cout << "层序遍历：" << endl;
    tree.LevelOrder();
    cout << endl;
    system("pause");
    return 0;
}

总结：二叉树有数组和链表的优点，二叉树的操作也很重要，这里用链表实现二叉树，借助队列实现了二叉树的层序遍历。