学步园

用c实现如下的二叉树

#include "stdio.h"
#include "malloc.h"
struct btree
{
	char data;
	struct btree *lp;
	struct btree *rp;
};
struct btree * init();
void pretraverse(struct btree *);
void intraverse(struct btree *);
void postraverse(struct btree *);
int main()
{
	struct btree * p=init();
	printf("前序遍历的结果为:\n");
	pretraverse(p);
	printf("中序遍历的结果为:\n");
	intraverse(p);
	printf("后序遍历的结果为:\n");
	postraverse(p);
	return 0;
}
struct btree * init()
{
	struct btree *a=(struct btree *)malloc(sizeof(struct btree));
	struct btree *b=(struct btree *)malloc(sizeof(struct btree));
	struct btree *c=(struct btree *)malloc(sizeof(struct btree));
	struct btree *d=(struct btree *)malloc(sizeof(struct btree));
	struct btree *e=(struct btree *)malloc(sizeof(struct btree));
	a->data='a';
	b->data='b';
	c->data='c';
	d->data='d';
	e->data='e';
	a->lp=b;
	b->lp=NULL;
	b->rp=NULL;
	a->rp=c;
	c->lp=d;
	d->lp=NULL;
	d->rp=NULL;
	c->rp=e;
	e->lp=NULL;
	e->rp=NULL;
	return a;
}
void pretraverse(struct btree *p)
{
	printf("%c\t",p->data);
	if(NULL!=p->lp)
	{
		pretraverse(p->lp);
	}
	if(NULL!=p->rp)
	{
		pretraverse(p->rp);
	}
}
void intraverse(struct btree *p)
{
	if(NULL!=p->lp)
	{
		intraverse(p->lp);
	}
	printf("%c\t",p->data);
	if(NULL!=p->rp)
	{
		intraverse(p->rp);
	}
}
void postraverse(struct btree *p)
{
	if(NULL!=p->lp)
	{
		postraverse(p->lp);
	}
	if(NULL!=p->rp)
	{
		postraverse(p->rp);
	}
	printf("%c\t",p->data);
}