/*第六题-先序、中序、后序遍历的递归算法*/
#include <stdio.h>
#include <stdlib.h>
#include <malloc.h>
#define OK 1
#define ERROR 0
#define NULL 0
#define OVERFLOW -2
typedef int Status;
typedef char TElemType;
/*二叉树的二叉链表存储表示*/
typedef struct BiTNode{
TElemType data;
struct BiTNode *lchild, *rchild; //左右孩子指针
}BiTNode, *BiTree;
/*建立二叉链表*/
Status CreateBiTree(BiTree &T){
//按先序次序输入二叉树中结点值，空格表示空树
//构造二叉链表表示的二叉树
char ch;
scanf("%c",&ch);
//ch=getchar();
if(ch==' ')
T=NULL;
else
{
if(!(T=(BiTNode*)malloc(sizeof(BiTNode)))) exit(OVERFLOW);
T->data=ch;
CreateBiTree(T->lchild);
CreateBiTree(T->rchild);
}
return OK;
}
/*打印二叉树的内容*/
Status PrintElement(char ch)
{
printf("%c",ch);
return OK;
}
/*先序遍历二叉树，递归算法*/
Status PreOrderTraverse(BiTree T,Status(*PrintElement)(TElemType e))
{
if(T)
{
if(PrintElement(T->data))
if(PreOrderTraverse(T->lchild,PrintElement))
if(PreOrderTraverse(T->rchild,PrintElement))
return OK;
return ERROR;
}
else return OK;
}
/*中序遍历二叉树，递归算法*/
Status InOrderTraverse(BiTree T,Status(*PrintElement)(TElemType e))
{
if(T)
{
if(InOrderTraverse(T->lchild,PrintElement))
if(PrintElement(T->data))
if(InOrderTraverse(T->rchild,PrintElement))
return OK;
return ERROR;
}
else return OK;
}
/*后序遍历二叉树，递归算法*/
Status PostOrderTraverse(BiTree T,Status(*PrintElement)(TElemType e))
{
if(T)
{
if(PostOrderTraverse(T->lchild,PrintElement))
if(PostOrderTraverse(T->rchild,PrintElement))
if(PrintElement(T->data))
return OK;
return ERROR;
}
else return OK;
}
int main()
{ BiTree T;
printf("请输入二叉树:");
printf("\n");
CreateBiTree(T);
printf("先序遍历:");
printf("\n");
PreOrderTraverse(T,PrintElement);
printf("\n");
printf("中序遍历:");
printf("\n");
InOrderTraverse(T,PrintElement);
printf("\n");
printf("后序遍历:");
printf("\n");
PostOrderTraverse(T,PrintElement);
printf("\n");
return 0;
}
