Löschen eines Bereichs von Knoten in C++

Question

Hallo, ich bin neu hier und relativ zu programmieren. Ich versuche, eine Reihe von Knoten in einer verknüpften Liste zu löschen, kann aber nicht herausfinden, wie das geht. Ich habe versucht, eine for-Schleife zu verwenden, aber da ich meine Löschfunktion eine Zeichenfolge übergeben, kann ich den Knoten nicht erhöhen, um es bis zur endgültigen Zählung zu löschen. Jede Hilfe würde sehr geschätzt werden!

#include <iostream> 
    #define nullptr 0 
    #include <cstdlib> 
    #include <algorithm> 
    #include <string> 
    #include <conio.h> 



    using namespace std; 
    int menu(); 

    class ItemList { 
     private: 
      struct ListNode{ 
       string IName; 
       string QQuantity; 
       string PPrice; 
       double value; 
       struct ListNode * next; 
        }; 
    ListNode *head; 
     public: 
      ItemList() 
       { 
        head = new ListNode; 
        head->next=nullptr; 
       } 
       ~ItemList(); 

       void insertNode(string Item, string Quantity, string Price) 
       { 
        ListNode *newNode; 
        ListNode *nodePtr; 
        ListNode *previousNode=nullptr; 

        newNode=new ListNode; 
        newNode->IName=Item; 
        newNode->QQuantity=Quantity; 
        newNode->PPrice=Price; 

        if(!head) 
        { 
         head=newNode; 
         newNode->next=nullptr; 
        } 
        else 
        { 
         nodePtr=head; 
         previousNode=nullptr; 

         while(nodePtr != nullptr && nodePtr->IName < Item) 
         { 
          previousNode=nodePtr; 
          nodePtr=nodePtr->next; 
         } 
         if(previousNode==nullptr) 
         { 
          head=newNode; 
          newNode->next=nodePtr; 
         } 
         else 
         { 
          previousNode->next=newNode; 
          newNode->next=nodePtr; 
         } 
        } 
       } 
       void displayNode() 
       { 
        ListNode *nodePtr; 
        nodePtr=head->next; 

        while(nodePtr) 
        { 
         cout << nodePtr->IName << ", "; 
         cout << nodePtr->QQuantity << " "; 
         cout << "$" << nodePtr->PPrice << "\n" << endl; 
         nodePtr=nodePtr->next; 
        } 
       } 
       void modifyNode(string Item) 
       { 
       ListNode *nodePtr; 
       ListNode *nodePrev; 
       string newName, newQuantity, newPrice; 
       int modify; 
       if (!head) 
       { 
        return; 
        cout << "Store is empty." << endl; 
       } 
       else 
       { 
        nodePtr = head; 
        if (head->IName==Item) 
         nodePtr = head->next; 
        else 
        { 
         while (nodePtr != nullptr && nodePtr->IName != Item) 
         { 
          nodePrev = nodePtr; 
          nodePtr = nodePtr->next; 
         } 
        } 
        if (nodePtr) 
        { 
         cout << nodePtr->IName << "\t" << nodePtr->QQuantity << "\t" << nodePtr->PPrice << endl; 
         cout << "What would you like to change?\n"; 
         cout << "1. Item" << endl; 
         cout << "2. Quantity" << endl; 
         cout << "3. Price" << endl; 
         cout << "4. Whole Entry" << endl; 
         cin >> modify; 

         transform(newName.begin(), newName.end(), newName.begin(), ::toupper); 
         switch (modify) 
         { 
          case 1: 
           cout << "Change to what?\n"; 
           cin >> newName; 
           nodePtr->IName = newName; 
           break; 
          case 2: 
           cout << "Change to what?\n"; 
           cin >> newQuantity; 
           nodePtr->QQuantity = newQuantity; 
           break; 
          case 3: 
           cout << "Change to what?\n"; 
           cin >> newPrice; 
           nodePtr->PPrice = newPrice; 
           break; 
          case 4: 
           cout << "Change to what?\n"; 
           cin >> newName; 
           nodePtr->IName = newName; 
           cout << "Change to what?\n"; 
           cin >> newQuantity; 
           nodePtr->QQuantity = newQuantity; 
           cout << "Change to what?\n"; 
           cin >> newPrice; 
           nodePtr->PPrice = newPrice; 
         } 
        } 
        else 
         cout << "Person not found\n"; 
       } 
      } 

       void deleteNode(string Item) 
       { 
        ListNode *nodePtr; 
        ListNode *previousNode; 

        if(!head) 
         return; 
        if(head->IName==Item) 
        { 
         nodePtr=head->next; 
         delete head; 
         head=nodePtr; 
        } 
        else 
        { 
         nodePtr=head; 
         while(nodePtr!=nullptr && nodePtr->IName!=Item) 
         { 
          previousNode=nodePtr; 
          nodePtr=nodePtr->next; 
         } 
         if(nodePtr) 
         { 
          previousNode->next=nodePtr->next; 
          delete nodePtr; 
         } 
         else 
         { 
          cout << "Nothing to delete." << endl; 
         } 
        } 
       } 
      }; 


    ItemList::~ItemList() 
    { 
     ListNode *nodePtr; 
     ListNode *nextNode; 

     nodePtr=head; 
     while(nodePtr!=nullptr) 
     { 
      nextNode=nodePtr->next; 
      delete nodePtr; 
      nodePtr=nextNode; 
     } 
    } 

    int main() 
    { 
     ItemList pro; 
     int method; 
     while(method!=0) 
     { 
     int method=menu(); 
     system("cls"); 
     string It, Q, P; 
     switch(method) 
     { 
     case 1: 
      int count; 
      cout << "How many products would you like to put in?" << endl; 
      cin >> count; 
      system("cls"); 
      for(int i=0; i<count; i++) 
      { 
       cout << "Product #" << i + 1 << endl; 
       cout << "Enter the item name: "; 
       cin.sync(); 
       getline(cin,It); 
       transform(It.begin(), It.end(), It.begin(), ::toupper); 
       cout << "Enter the Quantity: "; 
       cin >> Q; 
       transform(Q.begin(), Q.end(), Q.begin(), ::toupper); 
       cout << "Enter the Price: "; 
       cin >> P; 
       pro.insertNode(It, Q, P); 
       cout << "\n"; 
      } 
      break; 

     case 2: 
      pro.displayNode(); 
      break; 

     case 3: 
      pro.displayNode(); 
      cout << "What product do you wish to modify? (by item name)" << endl; 
      cin.sync(); 
      getline(cin, It); 
      transform(It.begin(), It.end(), It.begin(), ::toupper); 
      system("cls"); 
      pro.modifyNode(It); 
      break; 

     case 4: 
      int del; 
      cout << "Do you wish to delete one product or more?" << endl; 
      cout << "1. One" << endl; 
      cout << "2. Range of Products" << endl; 
       cin >> del; 
       system("cls"); 
       switch(del) 
       { 
        case 1: 
         cout << "What product do you wish to delete? (by item name)" << endl; 
         pro.displayNode(); 
         cout << "\n"; 
         cin.sync(); 
         getline(cin,It); 
         transform(It.begin(), It.end(), It.begin(), ::toupper); 
         pro.deleteNode(It); 
         cout << "\n"; 
         break; 
        case 2: 
         int count; 
         cout << "How many?"; 
         cin >> count; 
         pro.displayNode(); 
         cout << "Starting where?" << endl; 
         cin >> It; 
         transform(It.begin(), It.end(), It.begin(), ::toupper); 
         for(int i=0; i<count; i++) 
         { 
          pro.deleteNode(It); 
          It(i); 
         } 
         break; 
       } 
      break; 

     case 5: 
      pro.~ItemList(); 
      cout << "All items deleted." << endl; 
      break; 

     case 0: 
      cout << "Exiting the program." << endl; 
      return 0; 
     } 
     system("pause"); 
     system("cls"); 
     } 
     return 0; 
    } 

    int menu() 
    { 
     string space1= "     "; 
     string space2= "         "; 
     int method; 
     cout << space1 << "What would you like to do to the Phone Book?" << endl; 
     cout << space2 << "1. Insert" << endl; 
     cout << space2 << "2. Display" << endl; 
     cout << space2 << "3. Modify" << endl; 
     cout << space2 << "4. Delete" << endl; 
     cout << space2 << "5. Empty" << endl; 
     cout << space2 << "0. Exit\n" << endl; 
     cout << space2; 
     cin >> method; 
     return(method); 
    } 

Answer 1

Anstelle von Knoten Name (Iname) zu löschen, können Sie eine Funktion machen, die den Knotenzeiger eines gegebenen Namen ruft und dann ändern ‚deleteNode‘ Funktion auf eine, die anstelle des Namens durch den Zeiger löscht. Außerdem sollte diese Funktion den nächsten Knotenzeiger (oder null, wenn kein anderes Element in der Liste vorhanden ist) zurückgeben, mit dem Sie die nachfolgenden Knoten löschen können.

EDIT: sehr grundlegende Codebeispiel:

char * get_pointer_by_name(string Name) 
{ 
    ListNode * curr_node = this->head; 

    while(curr_node != NULL) 
    { 
     if(curr_node->IName == Name) 
     { 
      return (char *) curr_node; 
     } 
     else 
     { 
      curr_node = curr_node->next; 
     } 
    } 

    // node not found 

} 

char * delete_node(char * pointer) 
{ 
    char * tmp = (char *) (ListNode *) pointer->next; // check this, it may be wrong 
    // this is a very simple and illustrative way to delete your node, not the right one 
    delete pointer; 
    // return the next node pointer 
    return tmp; 
} 

Sobald dies geschehen ist, alles, was Sie tun müssen, ist die Knoten, die Sie mit get_pointer_by_name löschen möchten() und ein paar Mal wiederholen löschen die verbleibenden Knoten, genau so:

char * tmp = get_pointer_by_name("name"); 

while(tmp != NULL && count > 0) 
{ 
    tmp = deleteNode(tmp); 
    count--; 
}