二叉樹的常見遍歷層次遍歷用隊列，深度遍歷非遞歸用棧
#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;
//返回指針
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;
}
//至今不明白爲什麼這樣可以
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);
}
//非遞歸實現三種查找
void firorderpri(NODE* Tree)
{
stack<NODE* > s;//定義棧
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);
}
}
//中序遍歷
void midorderpri(NODE* Tree)
{
stack<NODE* > s;
NODE* p;
int a[100];
for(int i=0;i<=99;i++) //第二次出棧時才訪問
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); //中序遍歷要求根結點在中間入棧
if(p->lchild!=NULL)
s.push(p->lchild);
}
else {
printf("%d ",p->key);
}
}
}
//後序遍歷
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); //後序遍歷要求先入棧
if(p->rchild!=NULL)
s.push(p->rchild);
if(p->lchild!=NULL)
s.push(p->lchild);
}
else {
printf("%d ",p->key);
}
}
}
//按層次遍歷
void QPrintfTree(NODE* Tree)
{
int in,ou;
in=ou=0;
NODE * array[100]; //定義隊列
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);
}
}
//遞歸實現三種遍歷
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);
}
//刪除樹
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();//建二叉樹
// QPrintfTree(Tree);//層次遍歷
// PrintfTree(Tree);//前序遍歷
mPrintfTree(Tree);//中序遍歷
/* lPrintfTree(Tree);//後序遍歷
MakeTree(tree);
QPrintfTree(tree);//層次遍歷
PrintfTree(tree);//前序遍歷*/
firorderpri(Tree);
printf("\n");
midorderpri(Tree);
printf("\n");
lastorderpri(Tree);
}