题目19 二叉树的镜像

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//1. 题目19 二叉树的镜像
// 请完成一个函数，输入一个二叉树，该函数输出它的镜像
// 时间复杂度：O(n), 空间复杂度：O(1)  --> 但是递归有一些函数形参等的消耗

void MirrorOfBinaryTree(BinarySeachTreeNode<int>* pRoot)
{
    if (NULL == pRoot || (NULL == pRoot->m_pLeftNode && NULL == pRoot->m_pRightNode))
    {
        return;
    }

    // 交换左右节点
    BinarySeachTreeNode<int>* pTmpNode = pRoot->m_pLeftNode;
    pRoot->m_pLeftNode = pRoot->m_pRightNode;
    pRoot->m_pRightNode = pTmpNode;

    if (pRoot->m_pLeftNode)
    {
        MirrorOfBinaryTree(pRoot->m_pLeftNode);
    }

    if (pRoot->m_pRightNode)
    {
        MirrorOfBinaryTree(pRoot->m_pRightNode);
    }
}

// 二叉树镜像：非递归
// 时间复杂度：O(n), 空间复杂度：O(n)
void MirrorOfBinaryTree_1(BinarySeachTreeNode<int>* pRoot)
{
    if (NULL == pRoot || (NULL == pRoot->m_pLeftNode && NULL == pRoot->m_pRightNode))
    {
        return;
    }

    queue<BinarySeachTreeNode<int>*> stQueue;
    stQueue.push(pRoot);    // 队列先进先出

    while (!stQueue.empty())
    {
        pRoot = stQueue.front();
        stQueue.pop();

        // 交换子节点
        BinarySeachTreeNode<int>* pTmpNode = pRoot->m_pLeftNode;
        pRoot->m_pLeftNode = pRoot->m_pRightNode;
        pRoot->m_pRightNode = pTmpNode;

        if (pRoot->m_pLeftNode)
        {
            stQueue.push(pRoot->m_pLeftNode);
        }

        if (pRoot->m_pRightNode)
        {
            stQueue.push(pRoot->m_pRightNode);
        }
    }
}

void MirrorOfBinaryTreeTestFunc()
{
    cout << "\n\n --------------- MirrorOfBinaryTreeTestFunc Start -------------->" << endl;
    int aiArray[] = {8, 6, 10, 5, 7, 9, 11, 12};
    int iLen = sizeof(aiArray) / sizeof(int);
    TRAVERSAL_ARRAY(aiArray, iLen);

    // 1.建立一个二叉树
    CBinarySearchTree<int>* pTree = new CBinarySearchTree<int>();
    if (NULL == pTree)
    {
        return;
    }

    for (int i = 0; i < iLen; i++)
    {
        pTree->Insert(aiArray[i]);
    }

    pTree->Traversal();
    pTree->Traversal(TRAVERSAL_TYPE_RECUR_PRE_ORDER);

    // 2.二叉树镜像
    const BinarySeachTreeNode<int>* pRoot = pTree->GetTreeRootNode();
    MirrorOfBinaryTree(const_cast<BinarySeachTreeNode<int>*>(pRoot));   // 去const属性
    pTree->Traversal();

    MirrorOfBinaryTree_1(const_cast<BinarySeachTreeNode<int>*>(pRoot));
    pTree->Traversal();

    // 3.释放内存
    SAVE_DELETE(pTree);

    cout << "\n\n --------------- MirrorOfBinaryTreeTestFunc End -------------->" << endl;

}