本篇文章小编将带大家一起回顾经典c++之构建先序二叉树，有兴趣的小伙伴一起来复习一下吧！
二叉树首先要解决构建问题，才能考虑后续的遍历，这里贴出通过先序构建二叉树，同时包含四种二叉树的遍历方法（先序，中序，后序，逐层）
第一、定义BinaryTreeNode 类
#include <iostream>
#include <string>
#include <queue>
using namespace std;
template<typename T >class BinaryTree;
template <typename T> class BinaryTreeNode {
public:
friend class BinaryTree<T>;
BinaryTreeNode() {
data = NULL;
lChild = rChild = NULL;
}
BinaryTreeNode(T newdata) {
this->data = newdata;
lChild = rChild = NULL;
}
T getData() {
return data;
}
BinaryTreeNode<T> * getLeftNode() {
return lChild;
}
BinaryTreeNode<T> * getRightNode() {
return rChild;
}
T data;
BinaryTreeNode<T>* lChild;
BinaryTreeNode<T>* rChild;
private:
};View Code
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第二、定义BinaryTree 类
template <typename T> class BinaryTree {
public:
BinaryTreeNode<T> *root;
char* p;
BinaryTree() { root = NULL; }
BinaryTree(T data) {
root = new BinaryTreeNode<T>(data);
root->lChild = NULL;
root->rChild = NULL;
}
~BinaryTree() {
delete root;
}
//构建二叉树并返回
BinaryTreeNode<T>* CreateTree() {
BinaryTreeNode<int>* bt = NULL;
char t;
cin >> t;
if (t == '#')
{
return NULL;
}
else {
int num = t - '0';
bt = new BinaryTreeNode<T>(num);
bt->lChild = CreateTree();
bt->rChild = CreateTree();
}
return bt;
}
//先序构建二叉树
BinaryTreeNode<T>* PreCreateTree() {
BinaryTreeNode<int>* bt = NULL;
if (this->root == NULL)
{
cout << "请输入根节点（#代表空树）:";
}
else {
cout << "请输入节点（#代表空树）:";
}
char t;
cin >> t;
if (t == '#')
{
return NULL;
}
else {
int num = t - '0';
bt = new BinaryTreeNode<T>(num);
if (this->root == NULL)
{
this->root = bt;
}
cout << bt->data << "的左孩子";
bt->lChild = PreCreateTree();
cout << bt->data << "的右边孩子";
bt->rChild = PreCreateTree();
}
return bt;
}
void preOderTraversal(BinaryTreeNode<T> *bt); //先序遍历
void inOrderTraversal(BinaryTreeNode<T> *bt); //中序遍历
void postOrderTraversal(BinaryTreeNode<T> *bt);//后序遍历
void levelTraversal(BinaryTreeNode<T> *bt); //逐层遍历
private:
};
template <typename T>
void BinaryTree<T>::preOderTraversal(BinaryTreeNode<T> *bt) {
if (bt)
{
cout << bt->data;
BinaryTree<T>::preOderTraversal(bt->getLeftNode());
BinaryTree<T>::preOderTraversal(bt->getRightNode());
}
}
template <typename T>
void BinaryTree<T>::inOrderTraversal(BinaryTreeNode<T> *bt) {
if (bt)
{
BinaryTree<T>::inOrderTraversal(bt->getLeftNode());
cout << bt->data;
BinaryTree<T>::inOrderTraversal(bt->getRightNode());
}
}
template <typename T>
void BinaryTree<T>::postOrderTraversal(BinaryTreeNode<T> *bt) {
if (bt)
{
BinaryTree<T>::postOrderTraversal(bt->getLeftNode());
BinaryTree<T>::postOrderTraversal(bt->getRightNode());
cout << bt->data;
}
}
template <typename T>
void BinaryTree<T>::levelTraversal(BinaryTreeNode<T> *bt) {
queue<BinaryTreeNode<T>*> que;
que.push(bt);
while (!que.empty())
{
BinaryTreeNode<T>* proot = que.front();
que.pop();
cout << proot->data;
if (proot->lChild != NULL)
{
que.push(proot->lChild);//左孩子入队
}
if (proot->rChild != NULL)
{
que.push(proot->rChild);//右孩子入队
}
}
}View Code
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第三、主程序运行
#include "pch.h"
#include <iostream>
#include "BinaryTree.h"
int main()
{
//场景测试2
BinaryTree<int> btree;
btree.PreCreateTree();//先序构建二叉树
cout << "先序遍历:";
btree.preOderTraversal(btree.root); cout << endl;//先序遍历
cout << "中序遍历:";
btree.inOrderTraversal(btree.root); cout << endl;//中序遍历
cout << "后序遍历:";
btree.postOrderTraversal(btree.root); cout << endl;//后序遍历
cout << "逐层序遍历:";
btree.levelTraversal(btree.root);
}View Code
最终测试运行截图
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