《剑指offer》学习之--二叉树

最新推荐文章于 2022-04-18 15:24:45 发布

Digital2Slave

最新推荐文章于 2022-04-18 15:24:45 发布

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分类专栏： Algorithm 文章标签：二叉树结构

本文链接：https://blog.youkuaiyun.com/tianzhaixing2013/article/details/26248921

Algorithm 专栏收录该内容

33 篇文章

订阅专栏

本文介绍如何判断一棵二叉树是否为另一棵二叉树的子结构，并提供两种实现二叉树镜像的方法：递归与迭代。通过具体函数实现，帮助读者理解算法细节。

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18树的子结构

输入两棵二叉树A和B，判断B是不是A的子结构。二叉树结点定义如下：

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

bool HasSubtreeCore(BinaryTreeNode* pRoot1, BinaryTreeNode* pRoot2);
bool DoesTree1HaveTree2(BinaryTreeNode* pRoot1, BinaryTreeNode* pRoot2);

bool HasSubtree(BinaryTreeNode* pRoot1, BinaryTreeNode* pRoot2)
{
    bool result = false;

    if(pRoot1 != NULL && pRoot2 != NULL)//鲁棒性
    {
        if(pRoot1->m_nValue == pRoot2->m_nValue)
            result = DoesTree1HaveTree2(pRoot1, pRoot2);
        if(!result)
            result = HasSubtree(pRoot1->m_pLeft, pRoot2);//左子树遍历
        if(!result)
            result = HasSubtree(pRoot1->m_pRight, pRoot2);//右子树遍历
    }

    return result;
}

bool DoesTree1HaveTree2(BinaryTreeNode* pRoot1, BinaryTreeNode* pRoot2)
{
    if(pRoot2 == NULL)
        return true;

    if(pRoot1 == NULL)
        return false;

    if(pRoot1->m_nValue != pRoot2->m_nValue)
        return false;

    return DoesTree1HaveTree2(pRoot1->m_pLeft, pRoot2->m_pLeft) &&
        DoesTree1HaveTree2(pRoot1->m_pRight, pRoot2->m_pRight);
}

19二叉树的镜像

①递归

void MirrorRecursively(BinaryTreeNode *pNode)
{
    if((pNode == NULL) || (pNode->m_pLeft == NULL && pNode->m_pRight))
        return;

    BinaryTreeNode *pTemp = pNode->m_pLeft;
    pNode->m_pLeft = pNode->m_pRight;
    pNode->m_pRight = pTemp;
    
    if(pNode->m_pLeft)
        MirrorRecursively(pNode->m_pLeft);  

    if(pNode->m_pRight)
        MirrorRecursively(pNode->m_pRight); 
}

②循环

void MirrorIteratively(BinaryTreeNode* pRoot)
{
    if(pRoot == NULL)
        return;

    std::stack<BinaryTreeNode*> stackTreeNode;
    stackTreeNode.push(pRoot);

    while(stackTreeNode.size() > 0)
    {
        BinaryTreeNode *pNode = stackTreeNode.top();
        stackTreeNode.pop();

        BinaryTreeNode *pTemp = pNode->m_pLeft;
        pNode->m_pLeft = pNode->m_pRight;
        pNode->m_pRight = pTemp;

        if(pNode->m_pLeft)
            stackTreeNode.push(pNode->m_pLeft);

        if(pNode->m_pRight)
            stackTreeNode.push(pNode->m_pRight);
    }
}