编程之美读书笔记---分层遍历二叉树

层序遍历一颗二叉树。给定一颗二叉树如下：

输出结果：

1

2 3

4 5 6

7 8

给出书上的两种实现：

#include <iostream>
#include <cstring>
#include <vector>
using namespace std;
struct node{
	int data;
	node* left;
	node* right;
};
void creattree(node* &root)
{
	root=new node;
	root->data=1;
	node* t2=new node;
	t2->data=2;
	root->left=t2;
	node* t3=new node;
	t3->data=3;
	root->right=t3;
	node* t4=new node;
	t4->data=4;
	t2->left=t4;
	node* t5=new node;
	t5->data=5;
	t2->right=t5;
	node* t6=new node;
	t6->data=6;
	t3->left=NULL;
	t3->right=t6;
	t6->left=t6->right=NULL;
	t4->left=t4->right=NULL;
	node* t7=new node;
	t7->data=7;
	t7->left=t7->right=NULL;
	t5->left=t7;
	node* t8=new node;
	t8->data=8;
	t8->left=t8->right=NULL;
	t5->right=t8;
}
int printatlevel(node* root,int level)
{
	if(!root||level<0)return 0;
	if(level==0){
		cout<<root->data<<" ";
		return 1;
	}
	return printatlevel(root->left,level-1)+printatlevel(root->right,level-1);
}
void printbylevel(node* root)
{
	for(int level=0;;level++)
	{
		if(!printatlevel(root,level))
			break;
		cout<<endl;	
	}
}
void destroy(node* root)
{
	if(root->left==NULL&&root->right==NULL){
		delete root;
		return ;
	}
	if(root->left)destroy(root->left);
	if(root->right)destroy(root->right);
	delete root;
}
void print_new(node * root)
{
	if(root==NULL)
		return ;
	vector<node*> vec;
	vec.push_back(root);
	int cur=0,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;
	}	
}
int main()
{
	node *root;
	creattree(root);
	//printatlevel(root,1);
	//printbylevel(root);
	print_new(root);
	destroy(root);      //回收由new分配的内存
	return 0;
}