Question

我需要创建一个删除功能，所以我一直在网上看，但我无法在我的程序中修复它。 //在defs.h

struct notesTree 
{
    int nProdID;
    int nQuan; 
    int balance;            //will be used in AVL only, and be ignored in other cases.
    notesTree* pLeftChild;
    notesTree* pRightChild;
};

//在storebin.cpp中

void RemoveNode(notesTree* n, int item)
{
    // Find the item 
    bool found = false;
    notesTree* predecessor=NULL;
    notesTree* current=n;
    if(current==NULL) return;
    while(current!=NULL)
    {
        if(current->nProdID==item)
        {
            predecessor = current;
            found = true;
            break;
        }
        else
        {
            predecessor = current;
            if(item > (current->nProdID))
                current=current->pRightChild;
            else
                current=current->pLeftChild;
        }
    }


    if(!found)
    {
        return;
    }
    // CASE 1: Removing a node with a single child
    if((current->pLeftChild==NULL && current->pRightChild != NULL) || (current->pLeftChild != NULL && current->pRightChild==NULL))
    {
        // Right Leaf Present, No Left Leaf
        if(current->pLeftChild==NULL && current->pRightChild != NULL)
        {
            // If predecessor's left tree equals Node n
            if(predecessor->pLeftChild==current)
            {
                // then predecessor's left tree becomes n's right tree
                // and delete n
                predecessor->pLeftChild=current->pRightChild;
                delete current;
                current=NULL;
                cout<<item<<" has been removed from the Tree."<<endl;
            }
            // If predecessor's right tree equals Node n
            else
            {
                // then predecessor's right tree becomes n's right tree
                // and delete n
                predecessor->pRightChild=current->pRightChild;
                delete current;
                current=NULL;
                cout<<item<<" has been removed from the Tree."<<endl;
            }
        }
        else // Left Leaf Present, No Right Leaf Present
        {
            if(predecessor->pLeftChild==current)
            {
                predecessor->pLeftChild=current->pLeftChild;
                delete current;
                current=NULL;
                cout<<item<<" has been removed from the Tree."<<endl;
            }
            else
            {
                predecessor->pRightChild=current->pLeftChild;
                delete current;
                current=NULL;
                cout<<item<<" has been removed from the Tree."<<endl;
            }
        }
        return;
    }
    // CASE 2: Removing a Leaf Node
    if(current->pLeftChild==NULL && current->pRightChild==NULL)
    {
        if(predecessor->pLeftChild==current)
            predecessor->pLeftChild=NULL;
        else
            predecessor->pRightChild=NULL;
        delete current;
        cout<<item<<" has been removed from the Tree."<<endl;
        return;
    }
    // CASE 3: Node has two children
    // Replace Node with smallest value in right subtree
    if(current->pLeftChild != NULL && current->pRightChild != NULL)
    {
        notesTree* check=current->pRightChild;
        if((current->pLeftChild==NULL)&&(current->pRightChild==NULL))
        {
            current=check;
            delete check;
            current->pRightChild==NULL;
            cout<<item<<" has been removed from the Tree."<<endl;
        }
        else // Right child has children
        {
            // If the node's right child has a left child
            // Move all the way down left to locate smallest element
            if((current->pRightChild)->pLeftChild!=NULL)
            {
                notesTree* leftCurrent;
                notesTree* leftCurrentPred;
                leftCurrentPred=current->pRightChild;
                leftCurrent=(current->pRightChild)->pLeftChild;
                while(leftCurrent->pLeftChild != NULL)
                {
                    leftCurrentPred=leftCurrent;
                    leftCurrent=leftCurrent->pLeftChild;
                }
                current->nProdID=leftCurrent->nProdID;
                delete leftCurrent;
                leftCurrentPred->pLeftChild==NULL;
                cout<<item<<" has been removed from the Tree."<<endl;
            }
            else
            {
                notesTree* temp=current->pRightChild;
                current->nProdID=temp->nProdID;
                current->pRightChild=temp->pRightChild;
                delete temp;
                cout<<item<<" has been removed from the Tree."<<endl;
            }
        }
        return;
    }
}

我称之为

void doReserveEvent(notesTree* &root, int eventCode)
{
    int tmpMSP = (eventCode % 10000)/10;
    int tmpSoLuong = eventCode%10;
    notesTree*pt;
    pt=TimMSP(root,tmpMSP);
    if(pt!=NULL)
    {
        pt->nQuan-=tmpSoLuong;
        if(pt->nQuan<=0)
        {
            RemoveNode(root,tmpMSP);
            return;
        }
    }

    //o
}

当我调试它时，它不起作用并显示root {nProdID = ??? nQuan = ???余额= ??? ..}。如果（current == NULL）返回，行是否错误;

Answer 1

在我看来，这里有一个问题

while(current!=NULL)
{
    if(current->nProdID==item)
    {
        predecessor = current; // <--- remove this line
        found = true;
        break;

当您找到项目时，您编写前身的方式始终等于当前。我想前一个应该等于当前的之前的值。

我在BST中的删除功能甚至不起作用

1 个答案: