笔试题：用二叉树构造双向链表

#include <iostream>
#include <string.h>
using namespace std;
struct Node
{
Node *left;//相当于双向链表的prev指针。
Node *right;//相当于双向链表的next指针。
char data;
Node(char d = char()):data(d),left(NULL),right(NULL){}
};

class MTree
{
public:
MTree():root(NULL){}
void Create_Tree(char *VLR,char *LVR)
{
int n = strlen(LVR);
Create_Tree(root,VLR,LVR,n);
}
void Create_Tree(Node *&t,char *VLR,char *LVR,int n)
{
//构造二叉树。
if(n==0)return ;
int i = 0;
while(VLR[0]!=LVR[i])i++;
t = new Node(VLR[0]);
Create_Tree(t->left,VLR+1,LVR,i);
Create_Tree(t->right,VLR+i+1,LVR+i+1,n-i-1);
}
void Create_DList(MTree &mt)
{
Node *pr = NULL;
Create_DList(root,pr,mt.root);
}
static void Printf(MTree &mt)
{//双向链表打印。
Node *p = mt.root;
while(p!=NULL)
{
cout<<p->data<<" ";
p=p->right;
}
}
private:
void Create_DList(Node *t,Node *&pr,Node *&mt)
{
//构造双向链表。
if(t==NULL)
{
return ;
}
Create_DList(t->left,pr,mt);
if(t!=NULL)
{
t->left=pr;
if(pr)
pr->right = t;
if(pr==NULL)mt=t;
}
if(pr!=NULL && pr->right==NULL)
{
pr->right=t;
t->left = pr;
}
pr = t;
Create_DList(t->right,pr,mt);
}

private:
Node *root;
};
int main()
{
char VLR[]="ABCDEFG";
char LVR[]="CBDAFEG";

MTree mt;
mt.Create_Tree(VLR,LVR);
MTree mtlist;
mt.Create_DList(mtlist);
MTree :: Printf(mtlist);
return 0;
}