二叉树的遍历：前序，中序，后序，层序－－包括递归和非递归实现

注意：程序申请的空间并没有释放^_^
/**//********************************************************************
created: 2005/12/30
created: 30:12:2005 10:39
filename: bintree.h
author: Liu Qi

purpose: 二叉树的3种遍历方式(包括非递归实现),前序，后序和中序，先访问根节点就是
前序(部分书籍称为先根遍历,个人觉得该说法更好^_^)，类似的，最后访问根节点就是后序
*********************************************************************/


#ifndef TREE_H
#define TREE_H


#include
#include
#include
#include
#include

using namespace std;



typedef int ElemType;

typedef struct treeT
{
ElemType key;
struct treeT* left;
struct treeT* right;
}treeT, *pTreeT;




/**//*===========================================================================
* Function name: visit
* Parameter: root:树根节点指针
* Precondition:
* Description:
* Return value:
* Author: Liu Qi, //-
===========================================================================*/
static void visit(pTreeT root)
{
if (NULL != root)
{
printf(" %d\n", root->key);
}
}



/**//*===========================================================================
* Function name: BT_MakeNode
* Parameter: target:元素值
* Precondition: None
* Postcondition: NULL != pTreeT
* Description: 构造一个tree节点，置左右指针为空，并且返回指向新节点的指针
* Return value: 指向新节点的指针
* Author: Liu Qi, [12/30/2005]
===========================================================================*/
static pTreeT BT_MakeNode(ElemType target)
{
pTreeT pNode = (pTreeT) malloc(sizeof(treeT));

assert( NULL != pNode );

pNode->key = target;
pNode->left = NULL;
pNode->right = NULL;

return pNode;
}


/**//*===========================================================================
* Function name: BT_Insert
* Parameter: target:要插入的元素值, pNode:指向某一个节点的指针
* Precondition: NULL != ppTree
* Description: 插入target到pNode的后面
* Return value: 指向新节点的指针
* Author: Liu Qi, [12/29/2005]
===========================================================================*/
pTreeT BT_Insert(ElemType target, pTreeT* ppTree)
{
pTreeT Node;

assert( NULL != ppTree );

Node = *ppTree;
if (NULL == Node)
{
return *ppTree = BT_MakeNode(target);
}

if (Node->key == target) //不允许出现相同的元素
{
return NULL;
}
else if (Node->key > target) //向左
{
return BT_Insert(target, &Node->left);
}
else
{
return BT_Insert(target, &Node->right);
}
}




/**//*===========================================================================
* Function name: BT_PreOrder
* Parameter: root:树根节点指针
* Precondition: None
* Description: 前序遍历
* Return value: void
* Author: Liu Qi, [12/29/2005]
===========================================================================*/
void BT_PreOrder(pTreeT root)
{
if (NULL != root)
{
visit(root);
BT_PreOrder(root->left);
BT_PreOrder(root->right);
}
}


/**//*===========================================================================
* Function name: BT_PreOrderNoRec
* Parameter: root:树根节点指针
* Precondition: Node
* Description: 前序(先根)遍历非递归算法
* Return value: void
* Author: Liu Qi, [1/1/2006]
===========================================================================*/
void BT_PreOrderNoRec(pTreeT root)
{
stack s;

while ((NULL != root) !s.empty())
{
if (NULL != root)
{
visit(root);
s.push(root);
root = root->left;
}
else
{
root = s.top();
s.pop();
root = root->right;
}
}
}



/**//*===========================================================================
* Function name: BT_InOrder
* Parameter: root:树根节点指针
* Precondition: None
* Description: 中序遍历
* Return value: void
* Author: Liu Qi, [12/30/2005]
===========================================================================*/
void BT_InOrder(pTreeT root)
{
if (NULL != root)
{
BT_InOrder(root->left);
visit(root);
BT_InOrder(root->right);
}
}


/**//*===========================================================================
* Function name: BT_InOrderNoRec
* Parameter: root:树根节点指针
* Precondition: None
* Description: 中序遍历,非递归算法
* Return value: void
* Author: Liu Qi, [1/1/2006]
===========================================================================*/
void BT_InOrderNoRec(pTreeT root)
{
stack s;
while ((NULL != root) !s.empty())
{
if (NULL != root)
{
s.push(root);
root = root->left;
}
else
{
root = s.top();
visit(root);
s.pop();
root = root->right;
}
}
}



/**//*===========================================================================
* Function name: BT_PostOrder
* Parameter: root:树根节点指针
* Precondition: None
* Description: 后序遍历
* Return value: void
* Author: Liu Qi, [12/30/2005]
===========================================================================*/
void BT_PostOrder(pTreeT root)
{
if (NULL != root)
{
BT_PostOrder(root->left);
BT_PostOrder(root->right);
visit(root);
}
}


/**//*===========================================================================
* Function name: BT_PostOrderNoRec
* Parameter: root:树根节点指针
* Precondition: None
* Description: 后序遍历,非递归算法
* Return value: void
* Author: Liu Qi, // [1/1/2006]
===========================================================================*/
void BT_PostOrderNoRec(pTreeT root)
{
stack s;
pTreeT pre=NULL;

while ((NULL != root) !s.empty())
{
if (NULL != root)
{
s.push(root);
root = root->left;
}
else
{
root = s.top();
if (root->right!=NULL && pre!=root->right){
root=root->right;
}
else{
root=pre=s.top();
visit(root);
s.pop();
root=NULL;
}
}
}
}
/**//*===========================================================================
* Function name: BT_LevelOrder
* Parameter: root:树根节点指针
* Precondition: NULL != root
* Description: 层序遍历
* Return value: void
* Author: Liu Qi, [1/1/2006]
===========================================================================*/
void BT_LevelOrder(pTreeT root)
{
queue q;
treeT *treePtr;

assert( NULL != root );

q.push(root);

while (!q.empty())
{
treePtr = q.front();
q.pop();
visit(treePtr);

if (NULL != treePtr->left)
{
q.push(treePtr->left);
}
if (NULL != treePtr->right)
{
q.push(treePtr->right);
}

}
}


#endif



测试代码

#include
#include
#include
#include "tree.h"

#define MAX_CNT 5
#define BASE 100

int main(int argc, char *argv[])
{
int i;
pTreeT root = NULL;

srand( (unsigned)time( NULL ) );

for (i=0; i

摘自ngaut的博客http://www.cppblog.com/ngaut/archive/2006/01/01/2351.aspx