【数据结构基础】线索二叉树（递归实现）

#pragma warning(disable:4996)
#include<stdio.h>
#include<stdlib.h>
typedef struct TreeNode {
char data;
struct TreeNode *lchild, *rchild;
int ltag, rtag;
}Tree,*BTree;
BTree Build_Tree(void) {
BTree T;
char ch;
scanf("%c", &ch);
if (ch == '#') {
T = NULL;
}
else {
T = (BTree)malloc(sizeof(Tree));
T->data = ch;
T->ltag = 0;
T->rtag = 0;
T->lchild = Build_Tree();
T->rchild = Build_Tree();
}
return T;
}
//先序线索化
void Pre_Thread(BTree cur, BTree *pre) {
if (cur && cur->ltag==0) {
printf("%c ", cur->data);
if (cur->lchild == NULL) {
cur->lchild = *pre;
(*pre)->ltag = 1;
cur->ltag = 1;
}
if (cur->rchild == NULL) {
cur->rtag = 1;
}
if (*pre && (*pre)->rtag == 1) {
(*pre)->rchild = cur;
}
*pre = cur;
Pre_Thread(cur->lchild, pre);
Pre_Thread(cur->rchild, pre);
}
}
//中序线索化
void In_Thread(BTree cur, BTree *pre) {
if (cur) {
In_Thread(cur->lchild, pre);
printf("%c ", cur->data);
if (cur->lchild==NULL) {
cur->lchild = *pre;
cur->ltag = 1;
}
if (cur->rtag == NULL) {
cur->rtag = 1;
}
if (*pre && (*pre)->rtag == 1) {
(*pre)->rchild = cur;
}
*pre = cur;
In_Thread(cur->rchild, pre);
}
}
//后序线索化
void Post_Thread(BTree cur, BTree *pre) {
if (cur) {
Post_Thread(cur->lchild, pre);
Post_Thread(cur->rchild, pre);
printf("%c ", cur->data);
if (cur->lchild == NULL) {
cur->lchild = *pre;
cur->ltag = 1;
}
if (cur->rchild == NULL) {
cur->rtag = 1;
}
if (*pre && (*pre)->rtag == 1) {
(*pre)->rchild = cur;
}
*pre = cur;
}
}
int main(void) {
BTree T,p=NULL;
T = Build_Tree();
Pre_Thread(T, &p);
//In_Thread(T, &p);
//Post_Thread(T, &p);
return 0;
}