如何在线索二叉树中添加结点？

#include"stdio.h"#include"stdlib.h"#include"string.h"typedef struct Threadnode { int ltag,rtag; char date[20]; struct Threadnode *lchild, *rchild; } Threadnode, *ThreadTree;ThreadTree pre=NULL;void visite(char * ch){ printf("\n输出节点信息:"); printf("%s",ch);}//初始化二叉树ThreadTree CreatThreadTree(char ch[]){ ThreadTree t; char ch1[20],ch2[20]; t=( ThreadTree )malloc(sizeof(Threadnode)); strcpy(t->date,ch); printf("\n请输入左子树的数值，结束输入0:\n"); scanf("%s",ch1); if(strcmp(ch1,"0")==0) { t->ltag=1; t->lchild=NULL; } else { t->ltag=0; t->lchild=CreatThreadTree(ch1); } printf("\n请输入右子树的数值，结束输入0:\n"); scanf("%s",ch2); if(strcmp(ch2,"0")==0) { t->rtag=1; t->rchild=NULL; } else {t->rtag=0; t->rchild=CreatThreadTree(ch2); } return t;}//建立中序线索二叉树算法实现void InThread (ThreadTree t) { if (t) { InThread(t->lchild); if (t->lchild==NULL) { t->ltag=1; t->lchild=pre; } if (t->rchild==NULL) t->rtag=1; if ((pre)&&(pre->rtag==1)) pre->rchild=t; pre=t; InThread (t->rchild); }}//在中序线索二叉树上寻找结点p的中序后继结点的算法:ThreadTree InPostNode(ThreadTree p){ ThreadTree post; post=p->rchild; if (p->rtag==0) while (post->ltag==0) post=post->lchild; return (post);}// 在中序线索二叉树上查找值为X的结点ThreadTree Search (ThreadTree t,char x[] ) { ThreadTree p; p=t; if (p) { while (p->ltag==0) p=p->lchild; while (p&&strcmp(p->date,x)!=0) p= InPostNode (p); } return p; }//在中序线索二叉树上寻找结点p的中序前驱结点的算法：ThreadTree InPreNode(ThreadTree p){ ThreadTree prel; prel=p->lchild; if (p->ltag==0) while (prel->rtag==0) prel= prel->rchild; printf("\n结点p的中序前驱结点信息！\n"); visite(prel->date); return(prel);}// 中序线索二叉树的遍历算法void InOrderTh ( ThreadTree t) { ThreadTree p; if (t) { p=t; while (p->ltag==0) p=p->lchild; while (p) { visite(p->date); p= InPostNode (p); } } }void main(){ ThreadTree t,p; char ch[20],x[20]; int flag=1; while(flag){ printf("\n请选择需要进行的操作:\n"); printf("\n1：创建二叉树\n"); printf("\n2：线索二叉树\n"); printf("\n3：中序线索二叉树\n"); printf("\n4：寻找结点p的中序前驱结点\n"); printf("\n5：寻找结点p的中序后继结点\n"); printf("\n6：查找值为X的结点\n"); printf("\n0：退出！\n\n"); scanf("%d",&flag); switch(flag){ case 1 : printf("\n开始创建二叉树\n"); printf("\n请输入一个数值:"); scanf("%s",ch); t=CreatThreadTree(ch); printf("\n\n\n\n\n");break; case 2: printf("\n开始线索二叉树！\n"); InThread (t) ;break; case 3: printf("\n中序线索二叉树！\n"); InOrderTh ( t) ;break; case 4://在中序线索二叉树上寻找结点p的中序前驱结点的算法： printf("\n输入P节点信息，以方便查找\n"); scanf("%s",x); printf("\n寻找结点p的中序前驱结点!\n"); p=Search (t,x) ; InPreNode( p); break; case 5://在中序线索二叉树上寻找结点p的中序后继结点的算法: printf("\n输入P节点信息，以方便查找!\n"); scanf("%s",x); printf("\n结点p的中序后继结点信息！\n"); printf("\n寻找结点p的中序后继结点!\n"); p=Search (t,x) ; p=InPostNode( p); visite(p->date); break; case 6:// 在中序线索二叉树上查找值为X的结点 printf("\n请输入查找的数值！\n"); scanf("%s",x); p=Search(t,x); if(p) printf("\n查找成功！\n\n"); else printf("\n查找失败！\n\n"); break; default:break; } if(flag!=0) printf("\n****************请选择操作*****************\n"); }}