二叉树的常见遍历

二叉树的常见遍历层次遍历用队列，深度遍历非递归用栈

#include <stdio.h>#include<malloc.h>#include<stack> using namespace std;struct node{int key;struct node* lchild;struct node* rchild;};typedef struct node NODE,*Ptree;//返回指针NODE * CreatTree(){NODE * Phead;int nodekey;scanf("%d",&nodekey);if(0==nodekey)return NULL;Phead=(NODE*)malloc(sizeof(NODE));if(NULL==Phead)return NULL;Phead->key=nodekey;Phead->lchild=CreatTree();Phead->rchild=CreatTree();return Phead;}//至今不明白为什么这样可以void MakeTree(NODE*& Tree){Tree=(NODE*)malloc(sizeof(NODE));if(Tree==NULL)return;int s;scanf("%d",&s);if(s==0){Tree=NULL;return;}Tree->key=s;MakeTree(Tree->lchild);MakeTree(Tree->rchild);}//非递归实现三种查找void firorderpri(NODE* Tree){stack<NODE* > s;//定义栈NODE* p=Tree;if(Tree==NULL)return;s.push(Tree);while(!s.empty()){p=s.top();s.pop();printf("%d ",p->key);if(p->rchild!=NULL)s.push(p->rchild);if(p->lchild!=NULL)s.push(p->lchild);}}//中序遍历void midorderpri(NODE* Tree){stack<NODE* > s;NODE* p;int a[100];for(int i=0;i<=99;i++)//第二次出栈时才访问a[i]=0;if(Tree==NULL)return;s.push(Tree);while(!s.empty()){p=s.top();s.pop();if(a[p->key]!=1){a[p->key]=1;if(p->rchild!=NULL)s.push(p->rchild);s.push(p);//中序遍历要求根结点在中间入栈if(p->lchild!=NULL)s.push(p->lchild);}else {printf("%d ",p->key);}}}//后序遍历void lastorderpri(NODE* Tree){stack<NODE* > s;NODE* p;int a[100];for(int i=0;i<=99;i++)a[i]=0;if(Tree==NULL)return;s.push(Tree);while(!s.empty()){p=s.top();s.pop();if(a[p->key]!=1){a[p->key]=1;s.push(p);//后序遍历要求先入栈if(p->rchild!=NULL)s.push(p->rchild);if(p->lchild!=NULL)s.push(p->lchild);}else {printf("%d ",p->key);}}}//按层次遍历void QPrintfTree(NODE* Tree){int in,ou;in=ou=0;NODE * array[100];//定义队列array[0]=Tree;while(ou<=in){if(array[ou]->lchild!=NULL)array[++in]=array[ou]->lchild;if(array[ou]->rchild!=NULL)array[++in]=array[ou]->rchild;printf("%d  ",array[ou++]->key);}}//递归实现三种遍历void PrintfTree(NODE* Tree){    if(NULL==Tree)return ;static int nth=0;nth++;printf("%dth is %d\n",nth,Tree->key);PrintfTree(Tree->lchild);PrintfTree(Tree->rchild);}void mPrintfTree(NODE* Tree){    if(NULL==Tree)return ;mPrintfTree(Tree->lchild);static int nmth=0;nmth++;printf("%dth is %d\n",nmth,Tree->key);mPrintfTree(Tree->rchild);}void lPrintfTree(NODE* Tree){    if(NULL==Tree)return ;lPrintfTree(Tree->lchild);lPrintfTree(Tree->rchild);printf("%dth is %d\n",nlth,Tree->key);}//删除树void deleteTree(NODE* Tree){if(Tree==NULL)return;NODE* l,*r;l=Tree->lchild;r=Tree->rchild;free(Tree);Tree=NULL;deleteTree(l);deleteTree(r);}void main(){NODE * Tree,*tree;Tree=CreatTree();//建二叉树// QPrintfTree(Tree);//层次遍历//PrintfTree(Tree);//前序遍历       mPrintfTree(Tree);//中序遍历/*lPrintfTree(Tree);//后序遍历MakeTree(tree);QPrintfTree(tree);//层次遍历PrintfTree(tree);//前序遍历*/firorderpri(Tree);printf("\n");midorderpri(Tree);printf("\n");lastorderpri(Tree);}