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。

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

struct BTree
{
BTree* pLeft;
BTree* pRight;
int value;
};
void InsertBTree(BTree* &pRoot, int val)
{
if (!pRoot)
{
pRoot=new BTree;
pRoot->pLeft=NULL;
pRoot->pRight=NULL;
pRoot->value=val;
}
else
{
if (val>pRoot->value)
{
InsertBTree(pRoot->pRight,val);
}
if (val<pRoot->value)
{
InsertBTree(pRoot->pLeft,val);
}
if (val==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<<"  ";
BTDeque.pop_front();
if (p->pLeft)
{
BTDeque.push_back(p->pLeft);
}
if (p->pRight)
{
BTDeque.push_back(p->pRight);
}
}
cout<<""<<endl;
}

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;
}