c++ - 二叉树搜索函数

Question

该程序应要求用户输入他或她要搜索的员工的 ID 号。如果找到，则显示该 ID 号的员工。我可以通过显示功能显示身份证号码和员工，但我不知道如何使搜索功能工作并显示员工。

二叉树

#ifndef BINARYTREE_H
#define BINARYTREE_H
#include <iostream>
using namespace std;

// This class is a template class that creates a binary
// tree that can hold values of any data type. It has 
// functions to insert a node, delete a node, display the
// tree In Order, Pre Order and Post Order, search for a 
// value, count the number of total nodes, left nodes, 
// and a function to determine the height of the tree.

template <class T>
class BinaryTree
{
private:
    struct TreeNode
    {
        T value;            // The value in the node
        TreeNode *left;     // Pointer to left child node
        TreeNode *right;    // Pointer to right child node
    };

    TreeNode *root;         // Pointer to the root node

    // Private member functions
    void insert(TreeNode *&, TreeNode *&);
    void destroySubTree(TreeNode *);
    void deleteNode(T, TreeNode *&);
    void makeDeletion(TreeNode *&);
    void displayInOrder(TreeNode *) const;
    void displayPreOrder(TreeNode *) const;
    void displayPostOrder(TreeNode *) const;

public:
    // Constructor
    BinaryTree()
    { root = NULL; }

    // Destructor
    ~BinaryTree()
    { destroySubTree(root); }

    // Binary tree operations
    void insertNode(T);
    bool searchNode(int);
    void remove(T);

    void displayPreOrder() const
    { displayPreOrder(root); }

    void displayInOrder() const
    { displayInOrder(root); }

    void displayPostOrder() const
    { displayPostOrder(root); }

};

//*********************************************************
// insert function accepts a TreeNode pointer and a       *
// pointer to a node. The function inserts the node into  *
// the tree pointer to by the TreeNode pointer. This      *
// function is call recursively.                          *
//*********************************************************
template <class T>
void BinaryTree<T>::insert(TreeNode *&nodePtr, TreeNode *&newNode)
{
    if (nodePtr == NULL)
        nodePtr = newNode;              // Insert the node
    else if (newNode->value < nodePtr->value)
        insert(nodePtr->left, newNode); // Search the left branch
    else
        insert(nodePtr->right, newNode);// Search the right branch
}

//*********************************************************
// insertNode creates a new node to hold item as its value*
// and passes it to the insert function.                  *
//*********************************************************
template <class T>
 void BinaryTree<T>::insertNode(T item)
 {
     TreeNode *newNode;     // Pointer to a new node

     // Create anew node and store num in it
     newNode = new TreeNode;
     newNode->value = item;
     newNode->left = newNode->right = NULL;

     // Insert the node
     insert(root, newNode);
 }

//**********************************************************
// destroySubTree is called by the destructor. It deletes  *
// all nodes in the tree.                                  *
//**********************************************************
template <class T>
void BinaryTree<T>::destroySubTree(TreeNode *nodePtr)
{
     if (nodePtr)
     {
         if (nodePtr->left)
             destroySubTree(nodePtr->left);
         if (nodePtr->right)
             destroySubTree(nodePtr->right);
         delete nodePtr;
     }
}

//**********************************************************
// searchNode determines if a value is present in the tree.*
// If so, the function returns true. Otherwise it returns  *
// false.
//**********************************************************
template <class T>
bool BinaryTree<T>::searchNode(T item)
{
    TreeNode *nodePtr = root;

    while (nodePtr)
    {
        if (nodePtr->value == item)
            return true;
        else if (item < nodePtr->value)
            nodePtr = nodePtr->left;
        else
            nodePtr = nodePtr->right;
    }
    return false;
}

//*********************************************************
// remove calls deleteNode to delete the node whode value *
// member is the same as num                              *
//*********************************************************
template <class T>
void BinaryTree<T>::remove(T item)
{
    deleteNode(item, root);
}

//*********************************************************
// deleteNode deletes the node whose value member is the  *
// same as num                                            *
//*********************************************************
template <class T>
void BinaryTree<T>::deleteNode(T item, TreeNode *&nodePtr)
{
    if (item < nodePtr->value)
        deleteNode(item, nodePtr->left);
    else if (item > nodePtr->value)
        deleteNode(item, nodePtr->right);
    else
        makeDeletion(nodePtr);
}

//*********************************************************
// makeDeletion takes a reference to apointer to the node *
// that is to be deleted. The node is removed and the     *
// branches of the tree below the node are reattached     *
//*********************************************************
template <class T>
void BinaryTree<T>::makeDeletion(TreeNode *&nodePtr)
{
    // Define a temporary pointer to use in reattaching
    // the left subtree
    TreeNode *tempNodePtr;

    if (nodePtr == NULL)
        cout << "Cannot delete empty node.\n";
    else if (nodePtr->right == NULL)
    {
        tempNodePtr = nodePtr;
        nodePtr = nodePtr->left;    // Reattach the left child
        delete tempNodePtr;
    }
    else if (nodePtr->left == NULL)
    {
        tempNodePtr = nodePtr;
        nodePtr = nodePtr->right;   // Reattach the right child
        delete tempNodePtr;
    } 

}
//*********************************************************
// The displayInOrder function displays the values in the *
// subtree pointed to by nodePtr, via inorder traversal   *
//*********************************************************
template <class T>
void BinaryTree<T>::displayInOrder(TreeNode *nodePtr) const
{
    if (nodePtr)
    {
        displayInOrder(nodePtr->left);
        cout << nodePtr->value.getEmpID() << "  "
             << nodePtr->value.getEmpName() << endl;
        displayInOrder(nodePtr->right);
    }
}
//*********************************************************
// The displayPreOrder function displays the values in the*
// subtree pointed to by nodePtr, via Preorder traversal  *
//*********************************************************
template <class T>
void BinaryTree<T>::displayPreOrder(TreeNode *nodePtr) const
{
    if (nodePtr)
    {
        cout << nodePtr->value.getEmpID() << "  "
             << nodePtr->value.getEmpName() << endl;
        displayInOrder(nodePtr->left);
        displayInOrder(nodePtr->right);
    }
}
//*********************************************************
// displayPostOrder function displays the values in the   *
// subtree pointed to by nodePtr, via Postorder traversal *
//*********************************************************
template <class T>
void BinaryTree<T>::displayPostOrder(TreeNode *nodePtr) const
{
    if (nodePtr)
    {
        displayInOrder(nodePtr->left);
        displayInOrder(nodePtr->right);
        cout << nodePtr->value.getEmpID() << "  "
             << nodePtr->value.getEmpName() << endl;
    }
}
#endif

员工信息

#ifndef EMPLOYEEINFO_H
#define EMPLOYEEINFO_H
#include <string>
#include <iostream>
using namespace std;

// This class has two data members to hold the employee ID
// and the name of the employee.

class EmployeeInfo
{
private:
    int empID;      // To hold employee ID number
    string empName; // To hold employee name

public:
    // Default Constructor
    EmployeeInfo();

    // Constructor
    EmployeeInfo(int, string);

    // Mutators
    void setEmpID(int);
    void setEmpName(string);

    // Accessors
    int getEmpID();
    string getEmpName();

    // Overloaded operator. This works directly with
    // the insert function of BinaryTree.h more specifically
    // line 71. *For my knowledge*
    bool operator < (const EmployeeInfo &e)
    {
        if (empID < e.empID)
            return true;
        return false;
    }

    // Overloaded operator for the search function
    bool operator == (const EmployeeInfo &e)
    {
        if (empID == e.empID)
            return true;
        return false;
    }

};
#endif

#include "EmployeeInfo.h"

//*********************************************************
// Default constructor intializes the data members        *
//*********************************************************
EmployeeInfo::EmployeeInfo()
{
    empName = "";
    empID = 0;  
}

//*********************************************************
// Constructor sets the data members                      *
//*********************************************************
EmployeeInfo::EmployeeInfo(int ID, string name)
{
    empName = name;
    empID = ID; 
}

//*********************************************************
// setEmpID stores the employee ID number                 *
//*********************************************************
void EmployeeInfo::setEmpID(int ID)
{
    empID = ID;
}

//*********************************************************
// setEmpName stores the full name of the employee        *
//*********************************************************
void EmployeeInfo::setEmpName(string name)
{
    empName = name;
}

//*********************************************************
// getEmpID returns the employee ID number                *
//*********************************************************
int EmployeeInfo::getEmpID()
{
    return empID;
}

//*********************************************************
// getEmpName returns the full name of the employee       *
//*********************************************************
string EmployeeInfo::getEmpName()
{
    return empName;
}

主要

#include "EmployeeInfo.h"
#include "BinaryTree.h"
#include <iostream>
using namespace std;

int main()
{

    // Create an instance of BinaryTree
    BinaryTree<EmployeeInfo> tree;

    // Create an EmployeeInfo object
    EmployeeInfo emp1(1021, "John Williams");
    EmployeeInfo emp2(1057, "Bill Witherspoon");
    EmployeeInfo emp3(2487, "Jennifer Twain");
    EmployeeInfo emp4(3769, "Sophia Lancaster");
    EmployeeInfo emp5(1017, "Debbie Reece");
    EmployeeInfo emp6(1275, "George McMullen");
    EmployeeInfo emp7(1899, "Ashley Smith");
    EmployeeInfo emp8(4218, "Josh Plemmons");    

    tree.insertNode(emp1);
    tree.insertNode(emp2);
    tree.insertNode(emp3);
    tree.insertNode(emp4);
    tree.insertNode(emp5);
    tree.insertNode(emp6);
    tree.insertNode(emp7);
    tree.insertNode(emp8);

    // Search for an employee
    char again = 'y';       // To hold yes
    int id;                 // To hold ID number from user

    cout << "Would you like to search for an employee?\n";
    cout << "Enter Y for yes or N for No: ";
    cin >> again;
    if (again)
    {
        do
        {
            cout << "Enter the ID number of the employee: ";
            cin >> id;
            // Create an EmployeeInfo object to store the user's 
            // search parameters
            EmployeeInfo info;
            info.setEmpID(id);

            // If search finds what the user entered display the 
            // corresponding employee
            if (tree.searchNode(info))
            {
                cout << info.getEmpName() << endl; // Not right?
            }
            else
                cout << "ID not found!" << endl;

            cout << "Would you like to search for an employee?\n";
            cout << "Enter Y for yes or N for No: ";
            cin >> again;
        }while (again == tolower('Y'));
    }


    // Display in order
    tree.displayInOrder();
    cout << endl;
    tree.displayPreOrder();
    cout << endl;
    tree.displayPostOrder();
}

好的，我更改了代码以使 bool 和 if (tree.searchNode(info)) 工作，但我认为 cout 语句不是正确的。有人可以查看我的 searchNode 函数以及我如何在 main 中调用它，让我知道我做错了什么吗？

Answer 1

问题出在这里

    info.setEmpID(1021);
    info.setEmpID(1057);
    info.setEmpID(2487);
    info.setEmpID(3769);
    info.setEmpID(1017);
    info.setEmpID(1275);
    info.setEmpID(1899);
    info.setEmpID(4218);

    info.setEmpName("John Williams");
    info.setEmpName("Bill Witherspoon");
    info.setEmpName("Jennifer Twain");
    info.setEmpName("Sophia Lancaster");
    info.setEmpName("Debbie Reece");
    info.setEmpName("George McMullen");
    info.setEmpName("Ashley Smith");
    info.setEmpName("Josh Plemmons"); 

您没有向 info 添加任何内容，但每次调用 setEmpName() 时，您都在更新 info 对象。

你可以在 searchNode 方法中做一些改变，如下所示

template <class T>

bool BinaryTree::searchNode(T &item){ 树节点 *nodePtr = root;

while (nodePtr)
{
    if (nodePtr->value == item)
    {
        item.setEmpName(nodePtr->value.getEmpName());
        return true;
    }
    else if (item < nodePtr->value)
        nodePtr = nodePtr->left;
    else
        nodePtr = nodePtr->right;
}
return false;

在main()方法中

do
        {
            cout << "Enter the ID number of the employee: ";
            cin >> id;
            BinaryTree<EmployeeInfo> temp;
            if ((temp=tree.searchNode(id))!=NULL) 
            {
                cout << temp.getEmpName() << endl;
            }
            else{
                cout<<"ID not found"<<endl;
             }
            cout << "Would you like to search for an employee?\n";
            cout << "Enter Y for yes or N for No: ";
            cin >> again;
        }while (again == tolower('Y'));

//新变化...将 searchNode(T) 的声明更改为 searchNode(T &)...在您的新代码中，未在 info< 中设置找到的员工姓名 这就是为什么当您尝试打印 EmpName 时没有输出...因此更改是将 EmployeeInfo 的引用传递给 searchitem(T & )

模板bool BinaryTree::searchNode(T &item){ 树节点 *nodePtr = root;

while (nodePtr)
{
    if (nodePtr->value == item)
    {
        item.setEmpName(nodePtr->value.getEmpName());
        return true;
    }
    else if (item < nodePtr->value)
        nodePtr = nodePtr->left;
    else
        nodePtr = nodePtr->right;
}
return false;