从上到下打印二叉树——层序遍历二叉树

struct BinaryTreeNode
{
    int             m_nValue;
    BinaryTreeNode *m_pLeft;
    BinaryTreeNode *m_pRight;
};

void PrintFromTopToBottom(BinaryTreeNode *pTreeRoot)
{
	if(!pTreeRoot)
		return;

	std::deque<BinaryTreeNode*> dequeTreeNode;

	dequeTreeNode.push_back(pTreeRoot);

	while(dequeTreeNode.size())
	{
		BinaryTreeNode *pNode = dequeTreeNode.front();
		dequeTreeNode.pop_front();

		printf("%d " , pNode->m_nValue);

		if(pNode->m_pLeft)
			dequeTreeNode.push_back(pNode->m_pLeft);

		if(pNode->m_pRight)
			dequeTreeNode.push_back(pNode->m_pRight);
	}
}