樹（此處以二叉搜索樹爲例）的按層遍歷 更改版本

#include <iostream>
#include <deque>

using namespace std;


struct BSTNode
{
	int      value;
	BSTNode* left;
	BSTNode* right;
	BSTNode()
	{
		value = 0;
		left  = NULL;
		right = NULL;
	}

};

deque<BSTNode*> sq;

void insert(BSTNode* &p, int elem)
	{
		if(p == NULL)
		{
			BSTNode* pnew = new BSTNode();
			pnew->left = 0;
			pnew->right =0;
			pnew->value = elem;
			p = pnew;
			return;
		}
		if(elem > p->value)
		{
			insert(p->right, elem);
		}
		else if(elem < p->value)
		{
			insert(p->left, elem);
		}
		else
			cout << "The Same!" << endl;
	}

void BFS(BSTNode* root)
{
	BSTNode* p = root;
	sq.push_back(p);
	deque<BSTNode*>::iterator i = sq.begin();

	while(p != NULL)
	{	i++;
		sq.push_back(p->left);
		sq.push_back(p->right);
		p = *(i);
	}
}
void print_deque(deque<BSTNode*> que)
{
	deque<BSTNode*>::iterator iter = que.begin();
		for(; iter != que.end(); ++iter)
		{
			cout << (*iter)->value << endl;
		}
}

int main(void)
{
	BSTNode* root = 0;
	insert(root, 8);
	insert(root, 6);
	insert(root, 10);
	insert(root, 5);
	insert(root, 7);
	insert(root, 9);
	insert(root, 11);
	BFS(root);
	print_deque(sq);

	return 0;
}