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: };

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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 } }}

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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); }

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最终测试运行截图