《编程之美》3.10分层遍历二叉树

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

const int Max=30;
class Node
{
public:
	Node(int d):data(d),left(NULL),right(NULL){}
	int data;
	Node *left;
	Node *right;
};

template<class T>
class queue
{
public:
	queue(int i=Max):front(0),rear(0){Q=new T[Max];}
	void EnQueue(Node *p){Q[rear++] = p;}
	T DeQueue(){return Q[front++];}
	int front;
	int rear;
	T *Q;
};

int PrintNodeAtLevel(Node *root,int level)//递归
{
	if(!root || level<0)
		return 0;
	if(level==0)
	{
		cout<<root->data<<" ";
		return 1;
	}	
	PrintNodeAtLevel(root->left,level-1);
	PrintNodeAtLevel(root->right,level-1);
}
void PrintNode(Node *root)
{
	for(int level=0; ;level++)
	{
		if(!PrintNodeAtLevel(root,level))
			break;
		cout<<endl;
	}
}

void PrintNodeByLevel(Node *root)//非递归
{
	if(root==NULL)
		return;
	vector<Node *> vec;
	vec.push_back(root);
	int cur=0;
	int last=1;
	while(cur<vec.size())
	{
		last=vec.size();
		while(cur<last)
		{
			cout<<vec[cur]->data<<" ";
			if(vec[cur]->left)
				vec.push_back(vec[cur]->left);
			if(vec[cur]->right)
				vec.push_back(vec[cur]->right);
			cur++;
		}
		cout<<endl;
	}
}

void PrintNodeByBFS(Node *root) //BFS
{
	if(root==NULL)
		return;
	queue<Node *> que;
	que.EnQueue(root);
	Node *q;
	while(que.front<que.rear)
	{
		int	last=que.rear;
		while(que.front<last)
		{
			q=que.DeQueue();
			cout<<q->data<<" ";
			if(q->left)
				que.EnQueue(q->left);
			if(q->right)
				que.EnQueue(q->right);
		}
		cout<<endl;
	}
}
//扩展问题
/*
*依然是按层遍历二叉树，只是要求从下往上访问，并且每一层中结点的访问顺序为从右向左

*分析：只要层与层之间加入哑元素（NULL），然后逆序输出队列Q即可

*/
void PrintNodeDown2UpRight2Left(Node *root)
{
	if(root==NULL)
		return;
	queue<Node *> que;
	que.EnQueue(root);
	que.EnQueue(NULL);
	Node *q;
	while(que.front<que.rear-1)
	{
		int last=que.rear-1;
		while(que.front<last)
		{
			q=que.DeQueue();
			if(q->left!=NULL)
				que.EnQueue(q->left);
			if(q->right!=NULL)
				que.EnQueue(q->right);
		}
		que.EnQueue(NULL);//如果左右子树为空又多加入一个NULL
		que.front=last+1;
	}

	for(int i=que.rear-3;0<=i;i--)//逆序打印
	{
		if(que.Q[i]!=NULL)
			cout<<que.Q[i]->data<<" ";
		else
			cout<<endl;
	}
	cout<<endl;//只是为了排版

}

int main()
{
	Node *p1 = new Node(1);
    Node *p2 = new Node(2);
    Node *p3 = new Node(3);
    Node *p4 = new Node(4);
    Node *p5 = new Node(5);
    Node *p6 = new Node(6);
    Node *p7 = new Node(7);
    Node *p8 = new Node(8);
    p1->left = p2;
    p1->right = p3;
    p2->left = p4;
    p2->right = p5;
    p3->right = p6;
    p5->left = p7;
    p5->right = p8;
    Node *root = p1;
	//PrintNode(root);
    //PrintNodeByLevel(root);
	//PrintNodeByBFS(root);
	PrintNodeDown2UpRight2Left(root);
	return 0;
}