一步一步复习数据结构和算法基础-中序线索二叉树

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

typedef struct tree
{
int data;
struct tree *lchild,*rchild;

int lflag,rflag;			//左右标记：lflag=1当前节点左孩子指向前驱，
//rflag=1右孩子指向当前节点后继
}bitree,*ptree;

//先序创建二叉树
int creattree(ptree *T)
{
int data;
scanf("%d",&data);
if(data == 0)(*T) = NULL;
else
{
(*T) = (ptree)malloc(sizeof(bitree));
if(!(*T)){printf("operate error.\n");exit(1);}
(*T)->data = data;
(*T)->lflag = 0;		//树的节点左右标记为0
(*T)->rflag = 0;
creattree(&(*T)->lchild);
creattree(&(*T)->rchild);
}
return 1;
}

//中序线索二叉树
void inthreading(ptree root,ptree *pre)
{
if(root)
{
inthreading(root->lchild,&(*pre));
if(!root->lchild)
{
root->lchild = (*pre);
root->lflag = 1;
}
if(!(*pre)->rchild)
{
(*pre)->rchild = root;
(*pre)->rflag = 1;
}
(*pre) = root;
inthreading(root->rchild,&(*pre));
}
}

//建立头结点，中序线索二叉树
void inthreadingwithhead(ptree head,ptree root)
{
ptree pre;
head->lflag = head->rflag = 1;
head->data = 0;
head->rchild = head;
if(!root)
{
head->lchild = NULL;
}
else
{
head->lchild = root;
pre = head;
inthreading(root,&pre);
pre->rchild = head;
pre->rflag = 1;
head->rchild = pre;
}
}

//中序线索遍历二叉树
void inordertraverse(ptree head)
{

if(head)
{
if(head->lflag == 0)
inordertraverse(head->lchild);
printf("%d ",head->data);
if(head->rflag == 0)
inordertraverse(head->rchild);
}
return ;
}

int main()
{
ptree root;
bitree head;
creattree(&root);
inthreadingwithhead(&head,root);
printf("中序遍历结果为：\n");
inordertraverse(head.lchild);
printf("\n");
return 0;
}