Question

我使用BST实现了优先级队列。它的输出不正确。

输出：

Enter number of elements: 9
Enter number 1 of 9: 8
Enter number 2 of 9: 10
Enter number 3 of 9: 14
Enter number 4 of 9: 13
Enter number 5 of 9: 3
Enter number 6 of 9: 6
Enter number 7 of 9: 7
Enter number 8 of 9: 4
Enter number 9 of 9: 1
Outputting number 1 of 9: 14
Outputting number 2 of 9: 13
Outputting number 3 of 9: 10
Outputting number 4 of 9: 3
Outputting number 5 of 9: 3
Outputting number 6 of 9: 3
Outputting number 7 of 9: 3
Outputting number 8 of 9: 3
Outputting number 9 of 9: 3
Press any key to continue . . .

Test.cpp的

//Arkadiy Vasilkovskiy 832a1
#include <iostream>
#include "CTree.h"
#include "PriorityQueueBST.h"
using namespace std;

int main()
{

    int num, input, output;
    cout << "Enter number of elements: ";
    cin >> num;
    PriorityQueueBST p;
    for (int x = 0; x < num; x++)
    {
        cout << "Enter number " << x + 1  
            << " of " << num << ": ";
        cin >> input;
        p.Enqueue(input);
    }

    for (int y = 0; y < num; y++)
    {
        cout << "Outputting number " << y + 1  
            << " of " << num << ": ";
        if(p.IsEmpty())
        {
            break; //we are done (this is an error!)
        }

        output = p.Dequeue();
        cout << output << endl;
    }

    system("pause");
    return 0;
    //CTree* tr = new CTree();
    //
    //for (int i = 0; i < 3; i++)
    //  tr->Add();

    //tr->View();
    //system("pause");


    //return 0;
}

BST声明文件

struct TreeNode
{
    int info;
    TreeNode* leftLink;
    TreeNode* rightLink;
};


class CTree
{
public:
    CTree();
    ~CTree();
    void Add(int);
    void View();
    bool IsEmpty();
    int popLargest(TreeNode*);
    TreeNode *tree;


private:    
    void AddItem( TreeNode*&, TreeNode*);
    void DisplayTree(TreeNode*);
    void Retrieve(TreeNode*&, TreeNode*,bool&);
    void Destroy(TreeNode*&);
};

BST实施文件

#include <iostream>
#include <string>

using namespace std;

#include "CTree.h"

CTree::CTree()
{
    tree = NULL;
}

CTree::~CTree()
{
    Destroy(tree);
}

void CTree::Destroy(TreeNode*& tree)
{
    if (tree != NULL)
    {
    Destroy(tree->leftLink);
    Destroy(tree->rightLink);
    delete tree;
    }
}


bool CTree::IsEmpty()
{
    if(tree == NULL) 
    {
        return true;
    }
    else
    {
        return false;
    }
}

void CTree::Add(int dataToEnter)
{
    TreeNode* newPerson = new TreeNode();
    /*cout << "Enter the person's name: ";
    std::cin.ignore(std::numeric_limits<std::streamsize>::max(), '\n');
    cin.getline(newPerson->name, 20);*/
    //cout << "Enter the person's contribution: ";
    //cin >> newPerson->info;
    /*bool found = false;*/

    newPerson->info = dataToEnter;
    newPerson->leftLink = NULL;
    newPerson->rightLink = NULL;

    /*Retrieve(tree, newPerson, found);
     if (found)
         cout << "info allready entered\n";
     else*/
         AddItem(tree, newPerson);
}

void CTree::View()
{
    if (IsEmpty())
    {
        cout<<"The list is empy";
    }
    else
    {
        DisplayTree(tree);

    }

};

void CTree::AddItem( TreeNode*& ptr, TreeNode* newPer )
{
        if (ptr == NULL)
        {
            ptr = newPer;
        }
        else if ( newPer->info < ptr->info)
            AddItem(ptr->leftLink, newPer); 
        else
            AddItem(ptr->rightLink, newPer); 
}
void CTree::DisplayTree(TreeNode* ptr)
{
    if (ptr == NULL)
                    return;
    DisplayTree(ptr->rightLink);
    cout << ptr->info << endl; //cout<<ptr->name<<" "<<"$"<<ptr->info <<endl;
    DisplayTree(ptr->leftLink); 
}
void CTree::Retrieve(TreeNode*& ptr, TreeNode* newPer, bool& found)
{
    {
        if (ptr == NULL)
        {
            found = false; // item is not found.
        }
        else if ( newPer->info < ptr->info)
        {
            Retrieve(ptr->leftLink, newPer, found);
        }
             // Search left subtree.
        else if (newPer->info > ptr->info)
        {
            Retrieve(ptr->rightLink, newPer, found);// Search right subtree.
        }   
        else
        {
            //newPer.info = ptr->info; // item is found.
            found = true;
        }
    }
}

int CTree::popLargest(TreeNode* tr)
{
    //Failed Attempt at returning one value at a time and deleting that node
    int largest; // = tr->info;
    TreeNode* prev = NULL;
    TreeNode* cur = tr;

    if(tr != NULL)
        largest = tr->info;

    while (cur->rightLink != NULL)
    {
        prev = cur;
        cur = cur->rightLink;
        largest = cur->info;
        //DeleteAttemptTwo(tr, largest);//DeleteItem(largest);  

    }

    /*if (prev != NULL)
    {
        prev->rightLink = cur->leftLink;
    }*/

    if(prev != NULL)
    {
        if (cur->leftLink != NULL)
        {
            prev->rightLink = cur->leftLink;
        }
        else 
        {
            prev->rightLink = NULL;
        }
    }
    else if (cur->leftLink != NULL)
    {
        largest = cur->leftLink->info;
    }

    return largest;
}

优先级队列声明文件

#ifndef PRIORITYQUEUESLL__H
#define PRIORITYQUEUESLL__H

class PriorityQueueBST
{
    public:
        PriorityQueueBST();
        ~PriorityQueueBST();
        void Enqueue(int);
        int Dequeue();
        bool IsEmpty();

    private:
        CTree* ourTree;
};

#endif

优先级队列实施文件

#include <iostream>
using namespace std;
#include "CTree.h"
#include "PriorityQueueBST.h"

PriorityQueueBST::PriorityQueueBST()
{
    ourTree = new CTree();
    //head = NULL;
}

PriorityQueueBST::~PriorityQueueBST()
{

}

void PriorityQueueBST::Enqueue(int dataToEnter)
{
    ourTree->Add(dataToEnter);
}

int PriorityQueueBST::Dequeue()
{
    int largest = ourTree->popLargest(ourTree->tree);
    return largest;
}

bool PriorityQueueBST::IsEmpty()
{
    return ourTree->IsEmpty();

}

Answer 1

我运行了你的代码并查看了调试器中发生的事情。事实证明，当你弹出数字时，你的树就会被破坏。我基本上没有仔细研究它是如何发生的。在最初几次调用pop之前，你的树看起来像：

           8
    3            10
1      6              14
     4   7         13

在你弹出14,13,10后，它变成了：

现在如果我正确理解你的代码，那么逻辑错误就在这里：

if(prev != NULL)
{
    if (cur->leftLink != NULL)
    {
        prev->rightLink = cur->leftLink;
    }
    else 
    {
        prev->rightLink = NULL;
    }
}
else if (cur->leftLink != NULL)
{
    largest = cur->leftLink->info;
}

现在，如果您注意到最高数字是树的根（意味着prev == NULL），在这种情况下为8，则返回错误的值。你说最高值是左链接，但它不是根节点的值。 Wost，你永远不会把它从树上拿出来，所以你总是不停地给出相同的答案。

使用二进制搜索树的优先级队列不能产生正确的输出

1 个答案: