C++ 创建二叉树问题。。。

[ujn_uestc]

源代码：

#include "stdafx.h"

#include <iostream>
using namespace std;
typedef char elemtype;
struct node
{
elemtype data;
struct node *left;
struct node *right;
};



node * createbitr(node **r)
{
char ch;
cout<<"input the value of tree node "<<endl;
cin>>ch;
if (ch=='q')
*r=NULL;
else
if(!(*r=new node))
cout<<"内存分配失败"<<endl;
(*r)->data=ch;
createbitr(&(*r)->left);
createbitr(&(*r)->right);

return *r;
delete *r;
}


node * preorder(node **r)
{
if(*r)
{
cout<<(*r)->data<<'\t';
preorder(&(*r)->left);
preorder(&(*r)->right);
}
return *r;

}
int _tmain(int argc, _TCHAR* argv[])
{
node *root;
createbitr(&root);
preorder(&root);

return 0;
}


运行时有个警告：
bintree.cpp
c:\documents and settings\administrator.china-df4701fb0\桌面\bintree\bintree.cpp(34) : warning C4717: 'createbitr' : recursive on all control paths, function will cause runtime stack overflow
Linking...


运行时可以输入数据，但是退出时程序崩溃。。
大家帮忙改下嘛。。谢谢
本来程序只用的一重指针，参考了下
http://topic.csdn.net/u/20110103/20/71fbaa09-cf4c-4840-9a3a-da9b6ed222b9.html
改成跟他的差不多的，也没调出来。。帮忙看下，给我个可以完整调处结果的程序，谢谢了。。

[delphiwcdj]

[Quote=引用 7 楼 ujn_uestc 的回复:]

不对，你们的程序怎么都结束不了呢？？？- -
[/Quote]
应该这样输入：
比如二叉树为 1
/ \
2 3
/ \ / \
q q q q
即输入1 2 q q 3 q q
要按先序输入，这样才能结束……

[delphiwcdj]

乱了
应该这样输入：
比如二叉树为
1
/ \
2 3
/ \ / \
q q q q
即输入1 2 q q 3 q q
要按先序输入，这样才能结束……

[moorsf]

node * createbitr(node **r)
{
    char ch;
    cout<<"input the value of tree node "<<endl;
    cin>>ch;
    if (ch=='q') *r=NULL;
    else
    {
        if(!(*r=new node)) cout<<"内存分配失败"<<endl;
        else
        {
            (*r)->data=ch;
            createbitr(&(*r)->left);
            createbitr(&(*r)->right);
        }
    }

    return *r;
    //delete *r;
}

[ujn_uestc]

[Quote=引用 10 楼 delphiwcdj 的回复:]
乱了
应该这样输入：
比如二叉树为
1
/ \
2 3
/ \ / \
q q q q
即输入1 2 q q 3 q q
要按先序输入，这样才能结束……
[/Quote]

明白了，谢谢各位了^_^

[龙哥依旧]

#include "stdafx.h"
#include <iostream>
using namespace std;
typedef char elemtype;
struct node
{
    elemtype data;
    struct node *left;
    struct node *right;
};



node * createbitr(node **r)
{
    char ch;
    cout<<"input the value of tree node "<<endl;
    cin>>ch;
    if (ch=='q')
        *r=NULL;
    else
    {
        if(!(*r=new node))
            cout<<"内存分配失败"<<endl;
        (*r)->data=ch;
        createbitr(&(*r)->left);
        createbitr(&(*r)->right);
    }
        return *r;
//         delete *r;
}


node * preorder(node **r)
{
    if(*r)
    {
        cout<<(*r)->data<<'\t';
        preorder(&(*r)->left);
        preorder(&(*r)->right);
    }
    return *r;
    
}
int main(int argc, char* argv[])
{
    node *root;
    createbitr(&root);
    preorder(&root);
    
    return 0;
}

[delphiwcdj]

node * createbitr(node **r)
{
	char ch;
	cout<<"input the value of tree node "<<endl;
	cin>>ch;
	if (ch=='q')
		//*r=NULL;
		return NULL;
	else
	{
		if(!(*r=new node))
			cout<<"内存分配失败"<<endl;
	(*r)->data=ch;
	createbitr(&(*r)->left);
	createbitr(&(*r)->right);

	return *r;
	}
	//delete *r;
}

[無_1024]

[Quote=引用 2 楼 delphiwcdj 的回复:]
C# code

node * createbitr(node **r)
{
char ch;
cout<<"input the value of tree node "<<endl;
cin>>ch;
if (ch=='q')
//*r=NULL;
return NULL;
else
{
……
[/Quote]
+1赞同这种

[無_1024]

#include<stdio.h>
#include<malloc.h>
#define MaxSize 100
typedef struct node{
    char data;
    struct node *lchild;
    struct node *rchild;
}BTree;
void creatree(BTree *&b,char *str)//由广义表样式创建二叉树
{
    BTree *stack[MaxSize],*p;
    int top=-1,j=0;//栈空
    int k;//左右指标志
    char ch;
    b=NULL;
    ch=str[j];
    while(ch!='\0')
    {
        switch(ch)
        {
        case '(': top++;stack[top]=p;k=1;break;
        case ')': top--;break;
        case ',': k=2;break;
        default: p=(BTree*)malloc(sizeof(BTree));
                 p->data=ch;p->lchild=p->rchild=NULL;
                 if(b==NULL)
                     b=p;//根结点
                 else
                 {
                     if(k==1) stack[top]->lchild=p;
                     if(k==2) stack[top]->rchild=p;
                 }
        }
        j++;
  ch=str[j];
    }
}
void printree(BTree *b)//由广义表形式输出二叉树
{
    if(b!=NULL)
    {
        printf("%c",b->data);
        if(b->lchild!=NULL||b->rchild!=NULL)
        {
            printf("(");
            printree(b->lchild);
            if(b->rchild!=NULL)
            printf(",");
            printree(b->rchild);
            printf(")");
        }
    }
}
void Preorder(BTree *b){
  if(b!=NULL){
    printf("%c",b->data);
    Preorder(b->lchild);
    Preorder(b->rchild);
  }
}
void zhongxu(BTree *b){
   if(b){
      zhongxu(b->lchild);
      printf("%c",b->data);
      zhongxu(b->rchild);
   }
}

void houxu(BTree *b)
{
   if(b!=NULL){
     houxu(b->lchild);
     houxu(b->rchild);
     printf("%c",b->data);
  }
}

int Depth(BTree *b){
  int depl,depr;
  if(!b)
     return 0;
  else{
    depl=Depth(b->lchild);
    depr=Depth(b->rchild);
    return (depl>depr)?(depl+1):(depr+1);
  }

}

int main()
{
    BTree *b;
    creatree(b,"(A(B(,C),D(E,F)))");
    printf("广义表表示法为：\n");
    printree(b);
    system("pause");
}

[ujn_uestc]

[Quote=引用 2 楼 delphiwcdj 的回复:]
C# code

node * createbitr(node **r)
{
char ch;
cout<<"input the value of tree node "<<endl;
cin>>ch;
if (ch=='q')
//*r=NULL;
return NULL;
else
{
……
[/Quote]


好像不对，运行后提示一直输入，都退不出来了- -

[maoxing63570]

// csdn2.cpp : Defines the entry point for the console application.
//

#include "stdafx.h"

#include <iostream>
using namespace std;
typedef char elemtype;

struct node
{
	elemtype data;
	struct node *left;
	struct node *right;
};



void  createbitr(node **r)
{
	char ch;
	cout<<"input the value of tree node "<<endl;
	cin>>ch;
	if (ch=='q')
	{
		*r=NULL;
		return;
	}
	else
	{
		if(!(*r=new node))
		cout<<"内存分配失败"<<endl;
		(*r)->data=ch;
	}
	createbitr(&(*r)->left);
	createbitr(&(*r)->right);

	//return *r;
	//delete *r;
}


void  preorder(node *r)
{
	if(r)
	{
		cout<<r->data<<'\t';
		preorder(r->left);
		preorder(r->right);
	}
	//return *r;

}
int _tmain(int argc, _TCHAR* argv[])
{
	node *root=NULL;
	createbitr(&root);
	preorder(root);

return 0;
}

[ujn_uestc]

不对，你们的程序怎么都结束不了呢？？？- -

[ujn_uestc]

不过还是非常感谢大家给我的帮助。。^_^