双向链表C++用类

Question

我想创建一个双向链表实现：

class DblLinkedBag 
{ 
    private: 
    struct node{ 


    string data; 
    node* next; 
    node* prev; 
}*start=NULL; 

int itemCount; 
string item; 
    node *head; 
    node *tail; 



public: 
DblLinkedBag(); 
~DblLinkedBag();      
int getCurrentSize(); 
bool isEmpty(); 
string add(string value); 
bool remove(string item); 
void clear(); 
bool contains(string target); 
int getFrequencyOf(); 
string toVector(); 
string getItem(); 
void display(); 


}; 

到目前为止，我已经得到了补充，的isEmpty，getCurrentSize和明确的工作。现在我只需要其余的工作，我很难。我的教授给了我们一个要求，这个类必须像这样实现：

#include <iostream> 
    #include <string> 
    #include "LinkedBag.h" 

    using namespace std; 

    void displayBag(LinkedBag<string>& bag) 
{ 
cout << "The bag contains " << bag.getCurrentSize() 
    << " items:" << endl; 
vector<string> bagItems = bag.toVector(); 

int numberOfEntries = (int) bagItems.size(); 
for (int i = 0; i < numberOfEntries; i++) 
{ 
    cout << bagItems[i] << " "; 
} // end for 
cout << endl << endl; 
} // end displayBag 

    void copyConstructorTester() 
{ 
    LinkedBag<string> bag; 
string items[] = {"zero", "one", "two", "three", "four", "five"}; 
    for (int i = 0; i < 6; i++) 
    { 
     cout << "Adding " << items[i] << endl; 
    bool success = bag.add(items[i]); 
    if (!success) 
    cout << "Failed to add " << items[i] << " to the bag." << endl; 
} 
displayBag(bag); 

LinkedBag<string> copyOfBag(bag); 
cout << "Copy of bag: "; 
displayBag(copyOfBag); 

    cout << "The copied bag: "; 
displayBag(bag); 
    } // end copyConstructorTester 

void bagTester() 
{ 
LinkedBag<string> bag; 
cout << "Testing the Link-Based Bag:" << endl; 
cout << "isEmpty: returns " << bag.isEmpty() 
<< "; should be 1 (true)" << endl; 
    displayBag(bag); 

    string items[] = {"one", "two", "three", "four", "five", "one"}; 
    cout << "Add 6 items to the bag: " << endl; 
    for (int i = 0; i < 6; i++) 
    { 
    bag.add(items[i]); 
    } // end for 

    displayBag(bag); 

    cout << "isEmpty: returns " << bag.isEmpty() 
<< "; should be 0 (false)" << endl; 

cout << "getCurrentSize: returns " << bag.getCurrentSize() 
<< "; should be 6" << endl; 

cout << "Try to add another entry: add(\"extra\") returns " 
<< bag.add("extra") << endl; 

cout << "contains(\"three\"): returns " << bag.contains("three") 
<< "; should be 1 (true)" << endl; 
cout << "contains(\"ten\"): returns " << bag.contains("ten") 
<< "; should be 0 (false)" << endl; 
cout << "getFrequencyOf(\"one\"): returns " 
<< bag.getFrequencyOf("one") << " should be 2" << endl; 
cout << "remove(\"one\"): returns " << bag.remove("one") 
<< "; should be 1 (true)" << endl; 
cout << "getFrequencyOf(\"one\"): returns " 
<< bag.getFrequencyOf("one") << " should be 1" << endl; 
cout << "remove(\"one\"): returns " << bag.remove("one") 
<< "; should be 1 (true)" << endl; 
cout << "remove(\"one\"): returns " << bag.remove("one") 
<< "; should be 0 (false)" << endl; 
cout << endl; 

displayBag(bag); 

cout << "After clearing the bag, "; 
bag.clear(); 

cout << "isEmpty: returns " << bag.isEmpty() 
<< "; should be 1 (true)" << endl; 
} // end bagTester 

    int main() 
    { 
copyConstructorTester(); 
bagTester(); 
return 0; 
} // end main 

到目前为止，这是我的。

#include <iostream> 
#include <string> 
#include <vector> 
#include <stdio.h> 
#include <stdlib.h> 

using namespace std; 



    class DblLinkedBag 
{ 
    private: 
    struct node{ 


    string data; 
    node* next; 
    node* prev; 
    }*start=NULL; 

    int itemCount; 
    string item; 
    node *head; 
    node *tail; 



    public: 
DblLinkedBag(); 
~DblLinkedBag();      
int getCurrentSize(); 
bool isEmpty(); 
string add(string value); 
bool remove(string item); 
void clear(); 
bool contains(string target); 
int getFrequencyOf(); 
string toVector(); 
string getItem(); 
void display(); 


}; 


    DblLinkedBag::DblLinkedBag() 
{ 
    itemCount=0; 
    item; 
} 




string DblLinkedBag::add(string value) 
{ 

    node* n; 

     cout<<itemCount<<endl; 
     if(itemCount==0) 
{ 
    n=new node; 
    n->data=value; 
    n->prev=NULL; 
    head=n; 
    tail=n; 



    } 

if(itemCount>0 && itemCount<7) 
{ 
    n= new node; 
    n->data=value; 
    n->prev=tail; 
    tail->next=n; 
    tail=n; 


} 

    itemCount++; 
    return value; 
    } 

    void DblLinkedBag::display() 
{ 
struct node* temp=start; 
while(temp != NULL) 
{ 

cout<<temp->data<<endl; 
temp=temp->next; 
} 


} 



    int DblLinkedBag::getCurrentSize() 
    { 
return itemCount; 
} 



bool DblLinkedBag::contains(string target) 
    { 
    //need help here, supposed to tell if the linked list contains a certain //string 
    bool found= false; 
    node* curPtr=start; 
    int i=0; 

    while (!found && (curPtr!=NULL)&& (i<itemCount)) 
    { 

    if(target==curPtr->data) 
    { 
     found=true; 
    } 
    else 
    { 
     i++; 
     curPtr=curPtr->next; 
    } 
    } 
    return found; 
    } 
    bool DblLinkedBag::isEmpty() 
    { 
    bool empty; 
    if (itemCount==0) 
    { 
empty=true; 
} 

    else 
    empty=false; 

    return empty; 
} 

void DblLinkedBag::clear() 
{ 
    node* nodeToDelete=start; 
    while (start != NULL) 
{ 
    start=start->next; 
    nodeToDelete->next=NULL; 
    delete nodeToDelete; 
    } 
     itemCount=0; 
    } 

    bool DblLinkedBag::remove(string item) 
{ 
    //need help here 
} 
    string DblLinkedBag::toVector() 
    { 
    //need help here this is supposed to send the linked list to a vector 
    vector<string> vct; 
    node* curPtr= start; 
    int counter = 0; 
    while ((curPtr != NULL) && (counter < itemCount)) 
    { 
    vct.push_back(curPtr->data); 
    curPtr = curPtr->next; 
    counter++; 

} 

} 

int DblLinkedBag::getFrequency() 
{//supposed to show how many of a certain item are in the linked list 


DblLinkedBag::~DblLinkedBag() 
{ 
} 

任何执行这些类函数来创建其他功能我的教授给我将不胜感激的帮助下，我已经尝试了各种不同类型的实现，我似乎无法弄清楚。

Answer 1

首先：你的方法DblLinkedBag ::明确了一个错误，nodeToDelete永远不会改变（只是删除第一个节点）

bool DblLinkedBag::remove(string item) 
{ 
    node* curPtr=start; 

    while (curPtr!=NULL) 
    { 
     if(item==curPtr->data) 
     { 
      if(curPtr->prev) curPtr->prev->next = curPtr->next; 
      if(curPtr->next) curPtr->next->prev = curPtr->prev; 
      delete curPtr; 
      itemCount--; 
      return true; 
     } 
     else 
     { 
      curPtr=curPtr->next; 
     } 
    } 
    return false; 
} 

你有什么期望getFrequency（）做什么？