【剑指offer】面试题23：从上往下打印二叉树

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

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

};

void PrintFromTopToBottom(BinaryTreeNode* pTreeNode)
{
if (pTreeNode == NULL)
{
return;
}
//创建队列，将当前的结点的左右孩子指针分别放到容器中，方便使用
std::deque<BinaryTreeNode*>dequeTreeNode;

dequeTreeNode.push_back(pTreeNode);

//我们用队列来解决按层进行打印，也就是我们不需递归，每从队列中取出要打印的结点，并且把该节点的左右子结点保存到队列中即可
while (dequeTreeNode.size())
{
BinaryTreeNode* pNode = dequeTreeNode.front();

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

//该节点打印完后，我们进行弹出
dequeTreeNode.pop_front();

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

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

}

}
}