Table of contents
1. The structure of the binary tree
Second, the traversal method of the binary tree
- Preorder traversal: root –> left –> right
- Inorder traversal: left –> root –> right
- Post-order traversal: left –> right –> root
- Hierarchy traversal: top layer –> bottom layer
3. Source code
Note: For the implementation of the pre-order, in-order and post-order traversal algorithms in the binary tree, only the recursive method is used for the time being, and the non-recursive implementation method will be supplemented later.
/*
本项目主要用于二叉树的基础遍历算法测试。
1.binarytree.h包含对二叉树的结构体定义以及二叉树的先序、中序、后序以及层次遍历。
2.binarytree.cpp包含对各个遍历算法的实现。
3.main.cpp包含了对于二叉树遍历算法的测试。
*/
binarytree.h
#ifndef BINARYTREE_H
#define BINARYTREE_H
#include <QObject>
// 二叉树结点定义
struct TreeNode {
int data;
TreeNode* left;
TreeNode* right;
TreeNode(int val) : data(val), left(nullptr), right(nullptr) {
}
};
// 二叉树类
class BinaryTree : public QObject{
Q_OBJECT
public:
TreeNode* root;
int seq;
public:
BinaryTree();
/* 二叉树节点插入 */
void insertNode(int val);
/* 初始化二叉树 */
void initBinaryTree();
/* 二叉树先序遍历 */
void preOrderTravel(TreeNode* node);
/* 二叉树中序遍历 */
void inOrderTravel(TreeNode* node);
/* 二叉树后序遍历 */
void postOrderTravel(TreeNode* node);
/* 二叉树层次遍历 */
void levelOrderTravel();
};
#endif // BINARYTREE_H
binarytree.cpp
#include "binarytree.h"
#include <iostream>
#include <queue>
using namespace std;
BinaryTree::BinaryTree()
{
root = nullptr;
seq = 0;
}
// 插入结点
void BinaryTree::insertNode(int val) {
TreeNode* newNode = new TreeNode(val);
if (root == nullptr) {
root = newNode;
return;
}
TreeNode* curr = root;
while (true) {
if (val < curr->data) {
if (curr->left == nullptr) {
curr->left = newNode;
break;
} else {
curr = curr->left;
}
} else {
if (curr->right == nullptr) {
curr->right = newNode;
break;
} else {
curr = curr->right;
}
}
}
}
void BinaryTree::initBinaryTree()
{
int _data[7] = {
4,2,6,1,3,5,7};
cout<<"初始化节点序列：";
for(int i = 0;i < 7;i ++)
{
insertNode(_data[i]);
cout<<_data[i]<<" ";
}
cout<<endl;
}
void BinaryTree::preOrderTravel(TreeNode *node)
{
if (node == nullptr)
return;
cout<<"第"<<seq++<<"个节点："<<node->data<<endl;
if(node->left != nullptr)
preOrderTravel(node->left);
if(node->right != nullptr)
preOrderTravel(node->right);
}
void BinaryTree::inOrderTravel(TreeNode *node)
{
if (node == nullptr)
return;
if(node->left != nullptr)
inOrderTravel(node->left);
cout<<"第"<<seq++<<"个节点："<<node->data<<endl;
if(node->right != nullptr)
inOrderTravel(node->right);
}
void BinaryTree::postOrderTravel(TreeNode *node)
{
if (node == nullptr)
return;
if(node->left != nullptr)
postOrderTravel(node->left);
if(node->right != nullptr)
postOrderTravel(node->right);
cout<<"第"<<seq++<<"个节点："<<node->data<<endl;
}
void BinaryTree::levelOrderTravel()
{
if (root == nullptr)
return;
queue<TreeNode*> _q;
_q.push(root);
while(!_q.empty())
{
TreeNode* child = _q.front();
cout<<"第"<<seq++<<"个节点："<<child->data<<endl;
_q.pop();
if(child->left != nullptr)
_q.push(child->left);
if(child->right != nullptr)
_q.push(child->right);
}
cout<<endl;
}
main.cpp
#include <QCoreApplication>
#include <iostream>
#include <binarytree.h>
using namespace std;
int main(int argc, char *argv[])
{
QCoreApplication a(argc, argv);
BinaryTree *mTree = new BinaryTree;
cout<<"开始初始化二叉树!"<<endl;
mTree->initBinaryTree();//初始化二叉树
cout<<"开始执行二叉树的先序遍历!"<<endl;
mTree->preOrderTravel(mTree->root);
mTree->seq = 0;
cout<<"开始执行二叉树的中序遍历!"<<endl;
mTree->inOrderTravel(mTree->root);
mTree->seq = 0;
cout<<"开始执行二叉树的后序遍历!"<<endl;
mTree->postOrderTravel(mTree->root);
mTree->seq = 0;
cout<<"开始执行二叉树的层次遍历!"<<endl;
mTree->levelOrderTravel();
delete mTree;
mTree = nullptr;
return a.exec();
}
The effect is as follows:
