二叉树的先序，中序，后序递归遍历，以及计算节点的数目

方法一：

//用先序，中序，后序的方法递归遍历二叉树
#include<stdio.h>
#include<stdlib.h>
#include<malloc.h>

typedef int ElemType;

typedef struct node
{
ElemType data;
struct node *lchild,*rchild;
}BiNode,*Bitree;
//创建一个二叉树
void Inittree(Bitree e)
{
char x;
scanf("%d",&x);
if(x==0) e=NULL;
else
{
e=(BiNode *)malloc(sizeof(BiNode));
e->data=x;
Inittree(e->lchild);
Inittree(e->rchild);
}
}
//用先序遍历二叉树
void preorder(Bitree t)
{
if(t==NULL)
return ;
printf("%d\n",t->data);
preorder(t->lchild);
preorder(t->rchild);
}
//中序遍历二叉树
void Inorder(Bitree t)
{
if(t==NULL)
return ;
Inorder(t->lchild);
printf("%d\n",t->data);
Inorder(t->rchild);
}
//后序遍历二叉树
void posorder(Bitree t)
{
if(t==NULL)
return ;
posorder(t->lchild);
posorder(t->rchild);
printf("%d\n",t->data);
}
//用递归的方法计算二叉树的结点的个数
int countnode(Bitree t)
{
if(t==NULL)
return 0;
else
{
return countnode(t->lchild)+countnode(t->rchild)+1;
}
}

int main()
{
Bitree t;
int change=-1;
int num;
Inittree(t);
printf("1:先序遍历\n");
printf("2:中序遍历\n");
printf("3:后序遍历\n");
printf("4:计算树的结点个数\n");
printf("请输出选择:\n");
scanf("%d",&change);
switch(change)
{
case 1:
preorder(t);
printf("\n\n");
break;
case 2:
Inorder(t);
printf("\n\n");
break;
case 3:
posorder(t);
printf("\n\n");
break;
case 4:
countnode(t);
num=countnode(t);
printf("%d\n\n",num);
break;
default :
printf("ERROR!\n");
}
return 0;
}

 

 

 

 

 

 

 

 

 

 

 

 

方法二：

#include<stdio.h>
#include<stdlib.h>
#include<malloc.h>

//定义二叉树
typedef struct node{
int data;//数据元素
struct node *left;//指向左子树
struct node *right;//指向右子树
}BTree;

//构造二叉树：递归方式
int BTreeCreate(BTree **tp)
{
//构造方法，或者说构造顺序：从左子树开始构造
int x;
scanf("%d",&x);
if(x<=0)
{
*tp=NULL;//指针为空，树节点中的某个指针为空
return 0;
}
*tp=(BTree*)malloc(sizeof(BTree));//将树节点中指针指向该地址空间
if(tp==NULL)
return 0;
(*tp)->data=x;
BTreeCreate(&((*tp)->left));
BTreeCreate(&((*tp)->right));
return 1;
}

//遍历：前序遍历,递归的方式，先根节点，再左子树后右子树
void PreOrder(BTree *tree)
{
if(tree==NULL)
{
return;
}
printf("%d ",tree->data);
PreOrder(tree->left);
PreOrder(tree->right);
}

//遍历：中序遍历，递归方式，先左子树再根节点最后右子树
void MidOrder(BTree *tree)
{
if(tree==NULL)
{
return;
}
MidOrder(tree->left);
printf("%d ",tree->data);
MidOrder(tree->right);
}

//遍历：后序遍历，递归方式，先左子树再右子树最后根节点

void PostOrder(BTree *tree)
{
if(tree==NULL)
{
return;
}
PostOrder(tree->left);
PostOrder(tree->right);
printf("%d ",tree->data);
}

int countnode(BTree *tree)
{
if(tree==NULL)
return 0;
else
return countnode(tree->left)+countnode(tree->right)+1;
}

int main()
{
//二叉树构建
BTree *tree;
printf("Create binary tree:\n");
BTreeCreate(&tree);
//前序遍历
printf("Pre order:\n");
PreOrder(tree);
printf("\n");
//中序遍历
printf("Mid order:\n");
MidOrder(tree);
printf("\n");
//后序遍历
printf("Post order:\n");
PostOrder(tree);
printf("\n");
//计算二叉树节点数目
printf("输出点的数目:\n");
int num=countnode(tree);
printf("%d\n",num);

return 0;
}

转载于:https://www.cnblogs.com/-xss/p/5990879.html