C语言递归实现线索二叉树

#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;}