树的遍历实现，前序遍历，中序遍历，后序遍历以及层次遍历的迭代与递归实现

用C++实现了树的前序遍历，中序遍历，后序遍历以及层次遍历。分别用迭代与递归进行实现。(能够直接运行)代码如下：

//============================================================================// Name        : binaryTree.cpp// Author      : // Version     :// Copyright   : Your copyright notice// Description : Hello World in C++, Ansi-style//============================================================================#include <iostream>#include <stdlib.h>#include <stack>#include<queue>using namespace std;class BTree{public:int value;int id;bool visited;BTree* lChild;BTree* rChild;};BTree* btrees[100];int size;void buildTree(){cout<<"building a binary tree with "<<size<<" nodes"<<endl;int i;for(i=1;i<=size;i++){btrees[i]=new BTree;btrees[i]->value = rand()%100;btrees[i]->id = i;btrees[i]->visited = false;}int lchild,rchild;for(i=1;i<=size/2;i++){lchild=i*2;rchild=i*2+1;if(rchild<=size)btrees[i]->rChild = btrees[rchild];btrees[i]->lChild = btrees[lchild];}}void visit(BTree * tree){if(NULL!=tree){cout<<"visit node"<<tree->id<<"   value is  "<<tree->value<<endl;tree->visited= true;}}void preOrder(BTree *root){cout<<"preOrder"<<endl;if(NULL!=root){visit(root);preOrder(root->lChild);preOrder(root->rChild);}}void preOrderIter(BTree *root){cout<<"preOrderIter"<<endl;stack<BTree *> s;//s.push(root);while(!s.empty()||root!=NULL){if(root==NULL){root=s.top();s.pop();root=root->rChild;}else{visit(root);s.push(root);root= root->lChild;}}}void inOrder(BTree *root){cout<<"inorder"<<endl;if(NULL!=root){inOrder(root->lChild);visit(root);inOrder(root->rChild);}}void inOrderIter(BTree *root){cout<<"inOrderIter"<<endl;stack<BTree *> s;while(NULL!=root||!s.empty()){if(root!=NULL){s.push(root);root=root->lChild;}else{root = s.top();s.pop();visit(root);root=root->rChild;}}}void postOrder(BTree *root){cout<<"postOrder"<<endl;if(NULL!=root){postOrder(root->lChild);postOrder(root->rChild);visit(root);}}void postOrderIter(BTree *root){cout<<"postOrderIter"<<endl;stack<BTree*> s;s.push(root);while(root!=NULL&&!s.empty()){root=s.top();if((root->lChild==NULL&&root->rChild==NULL)||(root->lChild->visited==true&&root->rChild->visited==true)){s.pop();visit(root);}else{if(root->rChild)s.push(root->rChild);if(root->lChild!=NULL)s.push(root->lChild);}}}void levelOrder(BTree* root){cout<<"level order"<<endl;queue<BTree*> q;q.push(root);while(root!=NULL&&!q.empty()){root=q.front();q.pop();visit(root);if(root->lChild)q.push(root->lChild);if(root->rChild)q.push(root->rChild);}}int main() {//cout << "!!!Hello World!!!" << endl; // prints !!!Hello World!!!cout<<"input size of tree: ";cin>>size;cout<<endl;buildTree();//preOrder(btrees[1]);//inOrder(btrees[1]);//postOrder(btrees[1]);//preOrderIter(btrees[1]);//inOrderIter(btrees[1]);//postOrderIter(btrees[1]);levelOrder(btrees[1]);return 0;}