二叉树的操作

问题：再一次验证自己功底的薄弱，对那些大侠只有仰慕的份。。。

简单说一下自己的感受，递归的实现是个栈，每次函数结束时，退回到上一层，函数结束默认为return。

二叉树的各种非递归实现用到的数据结构是栈。

这次用重温了STL中stack的用法。

代码：

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

typedef struct node
{
	char data;
	struct node *left;
	struct node *right;
}*BinTree;

void CreateBTree(BinTree &btree)            //建立二叉树
{
	char c;
	btree=(BinTree)malloc(sizeof(struct node));
	cin>>c;
	if(!btree)
	{
		cout<<"allocated fail"<<endl;
		exit(-1);
	}
	if(c!='#')
	{
		btree->data=c;
		CreateBTree(btree->left);
		CreateBTree(btree->right);
	}
	else
	{
		btree=NULL;
	}

}
void showBTree(BinTree btree)   //递归前序遍历二叉树
{
	if(btree)
	{
		cout<<btree->data<<" ";
		showBTree(btree->left);
		showBTree(btree->right);
	}
}
void inOrderBTree(BinTree btree)  //递归中序遍历二叉树
{
	if(btree)
	{
		inOrderBTree(btree->left);
		cout<<btree->data<<" ";
		inOrderBTree(btree->right);

	}
}

void postOrderBTree(BinTree btree)  //递归后续遍历二叉树
{
	if(btree)
	{
		postOrderBTree(btree->left);
		postOrderBTree(btree->right);
		cout<<btree->data<<" ";
	}
}

void displayBTree(BinTree btree)   //非递归前序遍历二叉树
{
	stack<BinTree> q;
	if(btree)
	{
	BinTree bt;
	q.push(btree);
	while(!q.empty())
	{
		while(bt=q.top())
		{
			cout<<bt->data<<" ";
			q.push(bt->left);
		}
		q.pop();
		if(!q.empty())
		{
			bt=q.top();
			q.pop();
			q.push(bt->right);
		}
	}
	}
    
}

void iOrder(BinTree btree)  //中序非递归遍历
{
	BinTree bt=NULL;
	stack<BinTree> s;
	s.push(btree);
	while(!s.empty())
	{
		while(bt=s.top())
		{
			s.push(bt->left);
		}
		s.pop();
		if(!s.empty())
		{
			bt=s.top();
			cout<<bt->data<<" ";
			s.pop();
			s.push(bt->right);
		}
	}

}

void pOrder(BinTree btree)
{
	stack<BinTree> s;
	BinTree cur=NULL;
	BinTree pre=NULL;
	s.push(btree);
	while(!s.empty())
	{
		cur=s.top();
		if((cur->left==NULL&&cur->right==NULL)||(pre!=NULL&&(pre==cur->left||pre==cur->right)))
		{
			cout<<cur->data<<" ";
			s.pop();
			pre=cur;
		}
		else
		{
			if(cur->right)
				s.push(cur->right);
			if(cur->left)
				s.push(cur->left);		
		}
	}
}

int main()
{
	BinTree bt;
	cout<<"create bintree:"<<endl;
	CreateBTree(bt);

	cout<<"前序遍历二叉树:"<<endl;
	showBTree(bt);
	cout<<endl;
	cout<<"前序非递归遍历:"<<endl;
	displayBTree(bt);
	cout<<endl;

	cout<<"中序遍历二叉树:"<<endl;
	inOrderBTree(bt);
	cout<<endl;
	cout<<"中序非递归遍历二叉树："<<endl;
	iOrder(bt);
	cout<<endl;

	cout<<"后序遍历二叉树："<<endl;
	postOrderBTree(bt);
	cout<<endl;
	cout<<"后序非递归遍历:"<<endl;
	pOrder(bt);
	cout<<endl;
	return 0;
}

运行结果: