小程序（3）——二叉树遍历的非递归实现（三种遍历顺序）

本文介绍了如何使用栈非递归地实现二叉树的前序、中序和后序遍历。通过示例代码详细展示了每个遍历过程，并提供了相应的遍历函数。

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#ifndef __TREE_H
#define __TREE_H

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

struct BTree{
				int    data;
				BTree* left;
				BTree* right;
	};

void Pre_Order(BTree* rt)
{
	if(rt == NULL)
		return ;

	BTree* pNode = rt;
	stack<BTree*> S;

	while(!S.empty() || pNode != NULL)
	{
		while(pNode)
		{
			cout << pNode->data << "  ";
			S.push(pNode);
			pNode = pNode->left;
		}

		if(!S.empty())
		{
			pNode = S.top();
			S.pop();
			pNode = pNode->right;
		}
	}

	return ;
}


void In_Order(BTree* rt)
{
	if(rt == NULL)
		return ;

	BTree* pNode = rt;
	stack<BTree*> S;

	while(!S.empty() || pNode != NULL)
	{
		while(pNode)
		{
			S.push(pNode);
			pNode = pNode->left;
		}

		if(!S.empty())
		{
			pNode = S.top();
			cout << pNode->data << "  ";
			S.pop();
			pNode = pNode->right;
		}
	}

	return ;
}



void Post_Order(BTree* rt)
{
	if(rt == NULL)
		return ;

	BTree* pNode = rt;
	BTree* has_visite = NULL;
	stack<BTree*> S;

	while(!S.empty() || pNode != NULL)
	{
		while(pNode)
		{
			S.push(pNode);
			pNode = pNode->left;
		}

		if(!S.empty())
		{
			pNode = S.top();
			if(pNode->right == has_visite || pNode->right == NULL)
			{
				cout << pNode->data << "  ";
				has_visite = pNode;
				pNode = NULL;
				S.pop();
			}
			else
				pNode = pNode->right;
			
		}
	}

	return ;
}

#endif