【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

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/* 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)*/
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#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; 
}