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

typedef char DateType;

typedef struct Node
{
    DateType date;
    struct Node *lchild;
    struct Node *rchild;
}BiTreeNode;

void PrintDate(DateType x)
{
    printf("%c",x);
}

void CreatBiTree(BiTreeNode *T)
{
    DateType ch;
    scanf("%c",&ch);
    if(ch==' ')   {T=NULL;return;}
    else
    {
        if(!(T=(BiTreeNode*)malloc(sizeof(BiTreeNode)))){printf("Overflow.\n");exit(0);}
        (T)->date=ch;
        CreatBiTree(T->lchild);
        CreatBiTree(T->rchild);
    }
}

void PreOrder(BiTreeNode *T,void(*Visit)(DateType item))
{
    if(T!=NULL)
    {
        Visit(T->date);
        PreOrder(T->lchild,Visit);
        PreOrder(T->rchild,Visit);
    }
}

void InOrder(BiTreeNode *T,void(*Visit)(DateType item))
{
    if(T!=NULL)
    {
        InOrder(T->lchild,Visit);
        Visit(T->date);
        InOrder(T->rchild,Visit);
    }
}

void PostOrder(BiTreeNode *T,void(*Visit)(DateType item))
{
    if(T!=NULL)
    {
        PostOrder(T->lchild,Visit);
        PostOrder(T->rchild,Visit);
        Visit(T->date);
    }
}

void main()
{
    int choice;
    BiTreeNode *root;
    printf("下面建立一颗二叉树，结点数据输入顺序按先序次序\n");
    printf("输入数据请注意，每一个非空结点的所有还走都要给出\n");
    printf("如孩子为空，请用空格表示。\n");
    printf("请输入二叉树结点数据，这里设定为字符\n");
    CreatBiTree(root);
   
    printf("******************************\n");
    printf("         1.先序序列：\n");
    printf("         2.中序序列：\n");
    printf("         3.后序序列：\n");
    printf("         4.其他值则退出：\n");
    printf("******************************\n");

    do
    {
        printf("请输入对应的操作码：\n");
        scanf("%d",&choice);
        switch(choice)
        {
        case 1:printf("\n先序序列为:");
            PreOrder(root,PrintDate);printf("\n");break;
        case 2:printf("\n中序序列:");
            InOrder(root,PrintDate);printf("\n");break;
        case 3:printf("后序序列:");
            PostOrder(root,PrintDate);printf("\n");break;
        }
    }while(choice>0&&choice<4);
}