数据结构中树的创建和三种遍历方式的应用

自己对这一块的知识掌握的不是很好，所以就整理了一下，下面是代码；

#include<stdio.h>
#include<malloc.h>

typedef struct tree_node
{
	char data;
	struct tree_node *lchild,*rchild;
}BT_node;

BT_node *tree;


//树的创建
BT_node *creat_tree(BT_node *tree)
{
	char c;
	c = getchar();

	if(c == '*')
	{
		tree = NULL;
	}
	else
	{
		tree = (struct tree_node *)malloc(sizeof(struct tree_node));
		tree->data = c;
		tree->lchild = creat_tree(tree->lchild);
		tree->rchild = creat_tree(tree->rchild);
	}
	return(tree);
}

//遍历根节点
void visit_node(BT_node *tree)
{
	printf(" ");
	putchar(tree->data);
	printf("\t");
}


//前序遍历
void pre_tree(BT_node *tree)
{
	if(!tree)
	{
		return;
	}
	else
	{
		visit_node(tree);
		pre_tree(tree->lchild);
		pre_tree(tree->rchild);
	}
}

//中序遍历
void mid_tree(BT_node *tree)
{
	if(!tree)
	{
		return;
	}
	else
	{
		mid_tree(tree->lchild);
		visit_node(tree);
		mid_tree(tree->rchild);
	}
}

//后序遍历
void after_tree(BT_node *tree)
{
	if(!tree)
	{
		return;
	}
	else
	{	
		after_tree(tree->lchild);
		after_tree(tree->rchild);
		visit_node(tree);
	}
}


int main()
{
	printf("请输入树节点...\n");
	tree = creat_tree(tree);

	if(tree)
	{
		printf("前序遍历\n");
		pre_tree(tree);
		printf("\n");

		printf("中序遍历\n");
		mid_tree(tree);
		printf("\n");

		printf("后序遍历\n");
		after_tree(tree);
		printf("\n");
	}
	printf("\n");
	return 0;
}