复习，二叉树的非递归遍历，链栈实现

#include
using namespace std;

typedef struct LNode {
	char data;
	struct LNode* lchild, * rchild;
}LNode,*Tree;

typedef struct LNode_Stack{
	LNode* data;
	struct LNode_Stack* next;
}*Stack;//*不能忘记

void initStack(Stack& S) {
	S = NULL;
}
void push(Stack& S, LNode *p) {
	LNode_Stack* r = new LNode_Stack;
	r->data = p;
	r->next = S;
	S = r;
}
bool pop(Stack& S, Tree& p) {
	if (S == NULL)
		return false;
	else {
		p = S->data;
		S = S->next;
	}
	return true;
}
//这里的出栈问题要注意，不能用LNode
bool emptyStack(Stack S) {
	if (S == NULL)
		return true;
	return false;
}
void getStack(Stack S,Tree &p) {
	p = S->data;
}
void initTree(Tree& T) {
	T = NULL;
}
void buildTree_pre(Tree& T) {
	char e;
	cin >> e;
	if (e == '@')
		T = NULL;//递归出口
	else {
		T = new LNode;
		T->data = e;
		buildTree_pre(T->lchild);
		buildTree_pre(T->rchild);
	}
}
void visit(Tree T) {
	cout << T->data << " ";
}
void order_pre(Tree T) {
	if (T != NULL) {
		visit(T);
		order_pre(T->lchild);
		order_pre(T->rchild);
	}
}
void order_mid(Tree T) {
	if (T != NULL) {
		order_mid(T->lchild);
		visit(T);
		order_mid(T->rchild);
	}
}
void order_post(Tree T) {
	if (T != NULL) {
		order_post(T->lchild);
		order_post(T->rchild);
		visit(T);
	}
}

void ruTree_mid(Tree T,Stack &S) {
	while (T!= NULL) {
		push(S, T);
		T = T->lchild;
	}
}
//void order_no_mid(Tree T) {
//	Stack S;
//	initStack(S);
//	LNode* p = NULL;
//	ruTree_mid(T, S);
//	while (!emptyStack(S)) {
//		pop(S, p);
//		visit(p);
//		if (p->rchild)
//			ruTree_mid(p->rchild, S);
//	}
//}
void ruTree_pre(Tree T, Stack& S) {
	while (T != NULL) {
		visit(T);
		push(S, T);
		T = T->lchild;
	}
}
void order_no_pre(Tree T) {
	Stack S;
	initStack(S);
	LNode* p = NULL;
	ruTree_pre(T, S);
	while (!emptyStack(S)) {
		pop(S, p);
		//visit(p);
		if (p->rchild)
			ruTree_pre(p->rchild, S);
	}
}

//一直走到左下，若右子树不空，则将右子树重复
//出栈，访问
//先序遍历即先访问再入栈
void order_no_mid(Tree T) {
	Stack S;
	initStack(S);
	LNode* p = T;

	while (p||!emptyStack(S)) {
		if (p != NULL) {
			//visit(p);
			push(S, p);
			p = p->lchild;
		}
		else {
			pop(S, p);
			visit(p);
			p=p->rchild;
		}
	}
}
//一直走到左下，若右下不空且未访问，右子树重复
//出栈，访问，标记最近访问结点，置空
void order_no_post(Tree T) {
	Stack S;
	initStack(S);
	LNode* p = T;
	LNode* r = NULL;//visit的结点标记

	while (p || !emptyStack(S)) {
		if (p) {
			push(S, p);
			p = p->lchild;
		}
		else {
			getStack(S, p);
			if (p->rchild && p->rchild != r)
				p = p->rchild;
			else {
				pop(S, p);
				visit(p);
				r = p;
				p = NULL;//这里为什么要重置
			}
		}
	}
}

int main() {
	Tree T;
	initTree(T);
	buildTree_pre(T);
	//ab@@cd@@@@
	cout << "中序遍历" << endl;
	order_mid(T);
	cout << endl;

	cout << "后序遍历" << endl;
	order_post(T);
	cout << endl;

	cout << "先序遍历" << endl;
	order_pre(T);

	cout << endl;
	cout << "非递归中序遍历" << endl;
	order_no_mid(T);

	cout << endl;
	cout << "非递归先序遍历" << endl;
	order_no_pre(T);

	order_no_post(T);
	return 0;
}