关于二叉树四种遍历方式的核心代码

关于二叉树四种遍历方式的核心代码

1、前序遍历

//preOrder:
void PrintPreOrder(BinaryTreeNode* pNode)
{
	if (pNode == nullptr)
		return;
	BinaryTreeNode* pCurrent = pNode;
    std::cout << pCurrent->m_Value << " ";
	if (pCurrent->p_Left != nullptr)
		PrintPreOrder(pCurrent->p_Left);
    
    if (pCurrent->p_Right)
		PrintPreOrder(pCurrent->p_Right);
}

2、中序遍历

//InOrder:

void PrintInOrder(BinaryTreeNode* pNode)
{
	if (pNode == nullptr)
		return;
	BinaryTreeNode* pCurrent = pNode;
    
	if (pCurrent->p_Left != nullptr)
		PrintInOrder(pCurrent->p_Left);
    std::cout << pCurrent->m_Value << " ";
    if (pCurrent->p_Right)
		PrintInOrder(pCurrent->p_Right);
}

3、后序遍历

//postOrder:

void PrintPostOrder(BinaryTreeNode* pNode)
{
	if (pNode == nullptr)
		return;
	BinaryTreeNode* pCurrent = pNode;
	if (pCurrent->p_Left != nullptr)
		PrintPostOrder(pCurrent->p_Left);
    
    if (pCurrent->p_Right)
		PrintPostOrder(pCurrent->p_Right);
	std::cout << pCurrent->m_Value << " ";
}

4、层次遍历

void PrintLevelOrder(BinaryTreeNode* pRoot)
{
    if (pRoot == nullptr)
        return;
    BinaryTreeNode* pNode = nullptr;
    std::queue<BinaryTreeNode* > BinaryQueue;
    BinaryQueue.push(pRoot);
    int len = 1;
    while (BinaryQueue.size())//加入了len ,实现了分层的格式输出
    {
        if (len == 0)
        {
            len = BinaryQueue.size();
            std::cout << std::endl;
        }
        pNode = BinaryQueue.front();
        std::cout << pNode->m_Value << " ";
        len--;
        BinaryQueue.pop();
        if (pNode->p_Left)
            BinaryQueue.push(pNode->p_Left);
        if (pNode->p_Right)
            BinaryQueue.push(pNode->p_Right);
    }
}