【练习】输入一颗二元树，从上往下按层打印树的每个结点，同一层中按照从左往右的顺序打印

/************************************************************************/
/* 题目：输入一颗二元树，从上往下按层打印树的每个结点，同一层中按照从左往右的顺序打印。 
例如输入

8
/ \
6    10
/\     /\
5 7   9 11

输出8 6 10 5 7 9 11。

   思路：
   广度优先遍历
   
   deque(STL)*/
/************************************************************************/
#include <iostream>
#include <deque>
using namespace std;

 struct BTree 
{
	BTree* pLeft;
	BTree* pRight;
	int value;
};
void InsertBTree(BTree* &pRoot,int n)
{
	if(!pRoot)
	{
		pRoot=new BTree;
		pRoot->pLeft=NULL;
		pRoot->pRight=NULL;
		pRoot->value=n;
	}
	else
	{
		if (n>pRoot->value)
		{
			InsertBTree(pRoot->pRight,n);
		}
		if (n<pRoot->value)
		{
			InsertBTree(pRoot->pLeft,n);
		}
		if (n==pRoot->value)
		{
			cout<<"repeated insertion"<<endl;
		}
	}
}
void VisitByLevel(BTree* pRoot)
{
	if (!pRoot)
	{
		return;
	}
	deque<BTree*> BTDeque;
	BTDeque.push_back(pRoot);
	while(BTDeque.size())
	{
		BTree* p=BTDeque.front();
		cout<<p->value<<"\t";
		BTDeque.pop_front();
		if (p->pLeft)
		{
			BTDeque.push_back(p->pLeft);
		}
		if (p->pRight)
		{
			BTDeque.push_back(p->pRight);
		}
	}
}
int main()
{
	BTree* pRoot=NULL;
	InsertBTree(pRoot,8);
	InsertBTree(pRoot,6);
	InsertBTree(pRoot,10);
	InsertBTree(pRoot,5);
	InsertBTree(pRoot,7);
	InsertBTree(pRoot,9);
	InsertBTree(pRoot,11);
	VisitByLevel(pRoot);
	return 0;
}