二叉树的递归和非递归方式的三种遍历

#include <iostream>
#include <stack>
#include <vector>
using namespace std;

/*
  *输入样例 1 2 -1 -1 3 -1 -1
  *输入样例 1 2 3 -1 -1 4 -1 -1 5 6 -1 -1 7 -1 -1
  *输入样例 1 2 -1 3 -1 -1 4 5 -1 -1 -1
*/

struct Node {
	Node* left;
	Node* right;
	int data;
	Node(int x) :data(x), left(nullptr), right(nullptr) {};
};

void createBtiTree(Node* &root)
{
	int data;
	cin >> data;
	if (data == -1) {
		root = nullptr;
		return;
	}
	else {
		root = new Node(data);
		createBtiTree(root->left);
		createBtiTree(root->right);
	}
}

void visit(Node *T)
{
	if (T->data != -1)
		cout << T->data << " ";

}

//前序递归遍历
void preOrderRecur(Node* root)
{
	if (root == nullptr)
		return;	
	else
	{
		visit(root);
		preOrderRecur(root->left);
		preOrderRecur(root->right);
	}
}

//中序递归遍历
void inOrderRecur(Node* root)
{
	if (root == nullptr)
		return;
	else
	{
		inOrderRecur(root->left);
		visit(root);
		inOrderRecur(root->right);
	}
}


//后序递归遍历
void postOrder(Node * root)
{
	if (root != nullptr)
	{
		postOrder(root->left);
		postOrder(root->right);
		visit(root);
	}
}

//非递归前序遍历
void preOrderF(Node * root)
{
	if (root == nullptr)
		return;
	stack<Node *> s;
	s.push(root);
	Node *p = nullptr;
	while (!s.empty())
	{
		p = s.top();
		s.pop();
		visit(p);
		if (p->right)
			s.push(p->right);
		if (p->left)
			s.push(p->left);
	}
}

void preOrderF_2(Node *root)
{
		if (root == nullptr)
			return;
		stack<Node *> s;
		Node *p = root;
		while(p || !s.empty())
		{ 
			if (p)
			{
				visit(p);
				if (p->right)
					s.push(p->right);
				p = p->left;
			}
			else
			{
				p = s.top();
				s.pop();
			}
		}		
}

//非递归中序遍历
void inOrderF(Node * root)
{
	if (root == nullptr)
		return;
	stack<Node *> s;
	Node *p = root;
	while (p || !s.empty())
	{
		if (p)
		{
			s.push(p);
			p = p->left;
		}
		else
		{
			p = s.top();
			s.pop();
			visit(p);
			p = p->right;
		}
	}

}

//非递归后序遍历
void postOrderF(Node *root)
{
	if (root == nullptr)
		return;
	stack<Node *> s1;
	stack<Node *> s2;

	Node *p = nullptr;
	s1.push(root);
	while (!s1.empty())
	{
		p = s1.top();
		s1.pop();
		s2.push(p);
		if (p->left)
			s1.push(p->left);
		if (p->right)
			s1.push(p->right);
	}

	while (!s2.empty())
	{
		p = s2.top();
		visit(p);
		s2.pop();
	}
}

int main()
{
	Node *root;
	createBtiTree(root);
	
	cout << "递归前序遍历" << endl;
	preOrderRecur(root);
	cout << endl;
	cout << "------------------------"<<endl;
	

	cout << "递归中序遍历" << endl;
	inOrderRecur(root);
	cout << endl;
	cout << "------------------------" << endl;

	cout << "递归后序遍历" << endl;
	postOrder(root);
	cout << endl;
	cout << "------------------------" << endl;

	cout << "非递归前序遍历" << endl;
	preOrderF(root);
	cout << endl;
	cout << "------------------------" << endl;

	cout << "非递归中序遍历" << endl;
	inOrderF(root);
	cout << endl;
	cout << "------------------------" << endl;

	cout << "非递归后序遍历" << endl;
	postOrderF(root);
	cout << endl;
	cout << "------------------------" << endl;

	system("pause");
	return 0;
}