ARST 第五周打卡

Algorithm : 做一个 leetcode 的算法题

///////////////////////////////////////////////////////////////////
// 1. 与替换空格类似的题目
// 有两个排序数组A1， A2, A1的末尾有足够多的的空间容纳A2,实现一个函数，把A2中所有数字插入A1中且所有的数字的有序的！

//方法一：从前往后比较，需要额外的空间
//时间复杂度O(2n), 空间复杂度O(n)
void MergeTwoArray1(int aiArrayA[], int iNumA, int aiArrayB[], int iNumB)
{
    const int MAX_ARRAY_COUNT = iNumA + iNumB;
    vector<int> vect(MAX_ARRAY_COUNT, 0);

    int i = 0, j = 0, k = 0;
    
    // 1. 比较两个数组，把较小的加入新的数组
    while (i < iNumA &&j < iNumB)
    {
        if (aiArrayA[i] < aiArrayB[j])
        {
            vect[k++] = aiArrayA[i++];
        }
        else
        {
            vect[k++] = aiArrayB[j++];
        }
    }

    // 2.把剩余的元素加到新数组
    while (i < iNumA)
    {
        vect[k++] = aiArrayA[i++];
    }

    while (j < iNumB)
    {
        vect[k++] = aiArrayB[j++];
    }

    // 3.把数据复制到数组A
    k = 0;
    for (auto it : vect)
    {
        aiArrayA[k++] = it;
    }
}

// 方法二：从后往前比较，不需要额外的空间
//时间复杂度O(n), 空间复杂度O(1)
void MergeTwoArray2(int aiArrayA[], int iNumA, int aiArrayB[], int iNumB)
{
    int iNewNum = iNumA + iNumB - 1;
    int i = iNumA - 1;
    int j = iNumB - 1;
    
    // 从数组后往前比较，就不存在重叠的情况了！！！
    while (i >= 0 && j >= 0)
    {
        if (aiArrayA[i] > aiArrayB[j])
        {
            aiArrayA[iNewNum--] = aiArrayA[i--];
        }
        else
        {
            aiArrayA[iNewNum--] = aiArrayB[j--];
        }
    }

    while (i >= 0)
    {
        aiArrayA[iNewNum--] = aiArrayA[i--];
    }

    while (j >= 0)
    {
        aiArrayA[iNewNum--] = aiArrayB[j--];
    }

}

//////////////////////////////////////////////////////////////////////////////////////////////
// 2.题目五：从尾到头打印链表

// 方法一：时间复杂度O(n),空间复杂度O(n)
template <typename TYPE>
void ReversePrintList1(ListNode<TYPE>* pNode)
{
    assert(NULL != pNode);

    stack<ListNode<TYPE>*> stStack;
    while (pNode)
    {
        stStack.push(pNode);
        pNode = pNode->m_pNextNode;
    }
    
    cout << "链表逆序打印: " << endl;
    while (!stStack.empty())
    {
        ListNode<TYPE>* pTmpNode = stStack.top();
        printf("%02d -> ", pTmpNode->m_stData);
        stStack.pop();
    }

    putchar(10);

}

// 方法二：递归实现(递归实现也是类似栈实现)
// 时间复杂度O(n), 空间复杂度O(n)
// 注意：如果链表非常长，会导致函数调用层级很深，从而导致函数调用栈溢出！！！
template <typename TYPE>
void ReversePrintLisHEAP_TYPE(ListNode<TYPE>* pNode)
{
    if (!pNode)
    {
        return;
    }

    ReversePrintLisHEAP_TYPE(pNode->m_pNextNode);

    printf("%02d -> ", pNode->m_stData);
}

///////////////////////////////////////////////////////////////////////////////////////
// // 3.题目六：重建二叉树
// 题目:输入某二叉树的前序遍历和中序遍历的结果，请重建出改二叉树

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

    BinaryTreeNode(int iValue = 0, BinaryTreeNode* pLeft = NULL, BinaryTreeNode* pRight = NULL)
        :m_iValue(iValue), m_pLeft(pLeft), m_pRight(pRight)
    {

    }
};

BinaryTreeNode* RebuildTree(int* pPreStart, int* pPreEnd, int* pInStart, int* pInEnd)
{
    if (pPreStart > pPreEnd || pInStart > pInEnd)
    {
        return NULL;
    }

    // 1.建立根节点(前序遍历第一个元素)
    BinaryTreeNode* pRoot = new BinaryTreeNode(*pPreStart);
    if (!pRoot)
    {
        return NULL;
    }

    // 2.找到中序根节点
    int* p = pInStart;
    while (p <= pInEnd && *p != pRoot->m_iValue)
    {
        p++;
    }

    int iLeftLength = p - pInStart;
    int* pLeftPreEnd = pPreStart + iLeftLength;

    // 3.构建左子树
    if (iLeftLength > 0)
    {
        pRoot->m_pLeft = RebuildTree(pPreStart + 1, pLeftPreEnd, pInStart, p - 1);
    }

    // 4.构建右子树
    if (iLeftLength < (pPreEnd - pPreStart))
    {
        pRoot->m_pRight = RebuildTree(pLeftPreEnd + 1, pPreEnd, p + 1, pInEnd);
    }

    return pRoot;
}

BinaryTreeNode* RebuildBinaryTree(int* piPreOrderArray, int* piInorderArray, int iLength)
{
    if (NULL == piPreOrderArray || NULL == piInorderArray || iLength <= 0)
    {
        return NULL;
    }

    return RebuildTree(piPreOrderArray, piPreOrderArray + iLength - 1, piInorderArray, piInorderArray + iLength -1);
}

void DestroyTree(BinaryTreeNode* pTree)
{
    if (pTree)
    {
        // 释放左子树
        DestroyTree(pTree->m_pLeft);

        // 释放右子树
        DestroyTree(pTree->m_pRight);

        delete pTree;
        pTree = NULL;
    }
}

// 后序遍历
void PostTraversal(BinaryTreeNode* pNode)
{
    if (pNode)
    {
        PostTraversal(pNode->m_pLeft);
        PostTraversal(pNode->m_pRight);
        printf("%02d -> ", pNode->m_iValue);
    }
}

void RebuildBinaryTreeTestFunc()
{
    cout << "\n\n --------------- RebuildBinaryTreeTestFunc Start -------------->" << endl;
    const int MAX_TREE_NODE_COUNT = 8;

    //前序遍历序列(中 -> 左 -> 右)
    int aiPreOrderArray[MAX_TREE_NODE_COUNT] = {1, 2, 4, 7, 3, 5, 6, 8};

    //中序遍历序列(左 -> 中 -> 右)
    int aiInorderArray[MAX_TREE_NODE_COUNT] = {4, 7, 2, 1, 5, 3, 8, 6};

    //后序遍历序列(左 -> 右 -> 中)
    int aiPostArray[MAX_TREE_NODE_COUNT] = {7, 4, 2, 5, 8, 6, 3, 1};

    BinaryTreeNode* pTree1 = RebuildBinaryTree(aiPreOrderArray, aiInorderArray, MAX_TREE_NODE_COUNT);
    if (pTree1)
    {
        // 后序遍历
        PostTraversal(pTree1);
        putchar(10);

        // 施法资源
        DestroyTree(pTree1);
    }

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

}

////////////////////////////////////////////////////////////////////////////////////
// 4.题目七：用两个栈实现队列
// 题目：用两个栈实现一个队列，队列的声明如下：

template <typename TYPE>
class CQueue
{
public:
    CQueue(){}
    ~CQueue(){}

    void AppendTail(const TYPE& node);

    TYPE DeleteHead();

private:
    stack<TYPE> m_stPushStack;
    stack<TYPE> m_stPopStack;

};

// 方法一：
//    插入时 --> m_stPopStack不为空，将元素压入m_stPushStack；
//    删除时 --> m_stPushStack不为空，将元素压入 m_stPopStack；

// 方法二:
//    插入时 --> 直接往 m_stPushStack 插入新元素
//    删除时 --> 如果m_stPopStack为空，插入m_stPushStack中元素，否则直接弹出元素
template <typename TYPE>
TYPE CQueue<TYPE>::DeleteHead()
{
#if 0
    while (!m_stPushStack.empty())
    {
        m_stPopStack.push(m_stPushStack.top());
        m_stPushStack.pop();
    }

#else 
    if (m_stPopStack.empty())
    {
        while (!m_stPushStack.empty())
        {
            m_stPopStack.push(m_stPushStack.top());
            m_stPushStack.pop();
        }
    }

#endif

    TYPE tmp = m_stPopStack.top();
    m_stPopStack.pop();

    return tmp;
}

template <typename TYPE>
void CQueue<TYPE>::AppendTail(const TYPE& node)
{
#if 0
    while (!m_stPopStack.empty())
    {
        m_stPushStack.push(m_stPopStack.top());
        m_stPopStack.pop();
    }

    m_stPushStack.push(node);
#else

    m_stPushStack.push(node);

#endif 
}

void QueueWithTwoStackTestFunc()
{
    cout << "\n\n --------------- QueueWithTwoStackTestFunc Start -------------->" << endl;
    CQueue<int> stQueue;
    stQueue.AppendTail(1);
    stQueue.AppendTail(2);
    stQueue.AppendTail(3);
    cout << "Queue Pop Node: " << stQueue.DeleteHead() << endl;

    stQueue.AppendTail(4);
    stQueue.AppendTail(5);
    stQueue.AppendTail(6);
    cout << "Queue Pop Node: " << stQueue.DeleteHead() << endl;
    cout << "Queue Pop Node: " << stQueue.DeleteHead() << endl;
    cout << "Queue Pop Node: " << stQueue.DeleteHead() << endl;
    cout << "Queue Pop Node: " << stQueue.DeleteHead() << endl;
    cout << "Queue Pop Node: " << stQueue.DeleteHead() << endl;

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

}

/////////////////////////////////////////////////////////////////////////////////////////////
// 5.用两个队列实现一个栈

template <typename TYPE>
class CStack
{
public:
    CStack(){}
    ~CStack(){}

public:
    void AppendTail(const TYPE& value);

    TYPE DeleteHead();

private:
    queue<TYPE> m_stQueue1;
    queue<TYPE> m_stQueue2;
};

template <typename TYPE>
TYPE CStack<TYPE>::DeleteHead()
{
    TYPE head;
    if (m_stQueue1.empty())
    {
        while (m_stQueue2.size() > 1)
        {
            m_stQueue1.push(m_stQueue2.front());
            m_stQueue2.pop();
        }

        head = m_stQueue2.front();
        m_stQueue2.pop();
    }
    else
    {
        while (m_stQueue1.size() > 1)
        {
            m_stQueue2.push(m_stQueue1.front());
            m_stQueue1.pop();
        }

        head = m_stQueue1.front();
        m_stQueue1.pop();
    }

    return head;
}

template <typename TYPE>
void CStack<TYPE>::AppendTail(const TYPE& value)
{
    m_stQueue1.push(value);
}

void StackWithTwoQueueTestFunc()
{
    cout << "\n\n --------------- StackWithTwoQueueTestFunc Start -------------->" << endl;
    CStack<int> stStack;
    stStack.AppendTail(1);
    stStack.AppendTail(2);
    stStack.AppendTail(3);

    cout << "Stack Pop Node: " << stStack.DeleteHead() << endl;

    stStack.AppendTail(4);
    stStack.AppendTail(5);
    stStack.AppendTail(6);
    cout << "Stack Pop Node: " << stStack.DeleteHead() << endl;
    cout << "Stack Pop Node: " << stStack.DeleteHead() << endl;
    cout << "Stack Pop Node: " << stStack.DeleteHead() << endl;
    cout << "Stack Pop Node: " << stStack.DeleteHead() << endl;
    cout << "Stack Pop Node: " << stStack.DeleteHead() << endl;

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

}

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