二叉树的非递归遍历

#include<stdio.h>
#include<stdlib.h>
#define MAXSIZE 30
typedef struct node
{
	char data;
	struct node* lchild, * rchild;
}BSTree;
void Preorder(BSTree* p)//先序遍历
{
	BSTree* stack[MAXSIZE];
	int i = 0;
	stack[0] = NULL;
	while (p!=NULL||i>0)
	{
		if (p != NULL)
		{
			printf("%3c", p->data);
			stack[++i] = p;
			p = p->lchild;
		}
		else
		{
			p = stack[i--];
			p = p->rchild;
		}
	}
}
void Inorder(BSTree* p)//中序遍历
{
	BSTree* stack[MAXSIZE];
	int i = 0;
	stack[0] = NULL;
	while (i>=0)
	{
		if (p!=NULL)
		{
			stack[++i] = p;
			p = p->lchild;
		}
		else
		{
			p = stack[i--];
			printf("%3c", p->data);
			p = p->rchild;
		}
		if (p==NULL&&i==0)
		{
			break;
		}
	}
}
void Inorder2(BSTree* p)//中序遍历
{
	BSTree* stack[MAXSIZE];
	int i = 0;
	stack[0] = NULL;
	while (p!=NULL||i>0)
	{
		if (p != NULL)
		{
			stack[++i] = p;
			p = p->lchild;
		}
		else
		{
			p = stack[i--];
			printf("%3c", p->data);
			p = p->rchild;
		}
	}
}
void Postorder(BSTree* p)//后序遍历
{
	BSTree* stack[MAXSIZE];
	int i = 0,b[MAXSIZE];
	stack[0] = NULL;
	while (p != NULL || i > 0)
	{
		if (p!=NULL)
		{
			stack[++i] = p;
			b[i] = 0;
			p = p->lchild;
		}
		else
		{
			p = stack[i--];
			if (!b[i+1])
			{
				stack[++i] = p;
				p = p->rchild;
				b[i] = 1;
			}
			else
			{
				printf("%3c", p->data);
				p = NULL;
			}
		}
	} 
}
BSTree* Createb(BSTree** p)//创建二叉树
{
	char ch;
	scanf_s("%c", &ch);
	if (ch != '.')
	{
		(*p) = (BSTree*)malloc(sizeof(BSTree));
		(*p)->data = ch;
		(*p)->lchild = Createb(&(*p)->lchild);
		(*p)->rchild = Createb(&(*p)->rchild);
	}
	else
	{
		*p = NULL;
	}

	return *p;
}
void main(void)
{
	BSTree* root;
	printf("输入二叉树\n");
	Createb(&root);
	Preorder(root);
	printf("\n");
	Inorder(root);
	printf("\n");
	Inorder2(root);
	printf("\n");
	Postorder(root);
	printf("\n");
}