deleteNode - TTThiro/git GitHub Wiki

    Node(int value) {
        this->value = value;
        this->next = nullptr;
        this->prev = nullptr;
    }

public:
    DoublyLinkedList(int value) {
        Node* newNode = new Node(value);
        head = newNode;
        tail = newNode;
        length = 1;
    }

    ~DoublyLinkedList() {
        Node* temp = head;
        while (head) {
            head = head->next;
            delete temp;
            temp = head;
        }
    }

    void printList() {
        Node* temp = head;
        while (temp != nullptr) {
            cout << temp->value << endl;
            temp = temp->next;
        }
    }

    void getHead() {
        if (head == nullptr) {
            cout << "Head: nullptr" << endl;
        } else {
            cout << "Head: " << head->value << endl;
        }
    }

    void getTail() {
        if (tail == nullptr) {
            cout << "Tail: nullptr" << endl;
        } else { 
            cout << "Tail: " << tail->value << endl;
        }  
    }

    void getLength() {
        cout << "Length: " << length << endl;
    }

    void append(int value) {
        Node* newNode = new Node(value);
        if (length == 0) {
            head = newNode;
            tail = newNode;
        } else {
            tail->next = newNode;
            newNode->prev = tail;
            tail = newNode;
        }
        length++;
    }

    void deleteLast() {
        if (length == 0) return;
        Node* temp = tail;
        if (length == 1) {
            head = nullptr;
            tail = nullptr;
        } else {
            tail = tail->prev;
            tail->next = nullptr;
        }
        delete temp;
        length--;
    }

    void prepend(int value) {
        Node* newNode = new Node(value);
        if (length == 0) {
            head = newNode;
            tail = newNode;
        } else {
            newNode->next = head;
            head->prev = newNode;
            head = newNode;
        }
        length++;
    }

    void deleteFirst() {
        if (length == 0) return;
        Node* temp = head;
        if (length == 1) {
            head = nullptr;
            tail = nullptr;
        } else {
            head = head->next;
            head->prev = nullptr;
        }
        delete temp;            
        length--;
    }

    Node* get(int index) {
        if (index < 0 || index >= length) return nullptr;
        Node* temp = head;
        if (index < length/2) {
            for (int i = 0; i < index; ++i) {
                temp = temp->next;
            }
        } else {
            temp = tail;
            for (int i = length - 1; i > index; --i) {
                temp = temp->prev;
            }
        }
        return temp;
    }

    bool set(int index, int value) {
        Node* temp = get(index);
        if (temp) {
            temp->value = value;
            return true;
        }
        return false;
    }

    bool insert(int index, int value) {
        if (index < 0 || index > length) return false;
        if (index == 0) {
            prepend(value);
            return true;
        } 
        if (index == length) {
            append(value);
            return true;
        } 

        Node* newNode = new Node(value);
        Node* before = get(index - 1);
        Node* after = before->next;
        newNode->prev = before;
        newNode->next = after;
        before->next = newNode;
        after->prev = newNode;
        length++;
        return true;
    }       

    void deleteNode(int index) {
        if (index < 0 || index >= length) return;
        if (index == 0) return deleteFirst();
        if (index == length - 1) return deleteLast();
        
        Node* temp = get(index);

        temp->next->prev = temp->prev;
        temp->prev->next = temp->next;
        delete temp;
        length--;
    }

DoublyLinkedList* myDLL = new DoublyLinkedList(1);
myDLL->append(2);
myDLL->append(3);
myDLL->append(4);
myDLL->append(5);


cout << "DLL before deleteNode():\n";
myDLL->printList();


myDLL->deleteNode(2);
cout << "\nDLL after deleteNode() in middle:\n";
myDLL->printList();


myDLL->deleteNode(0);
cout << "\nDLL after deleteNode() of first node:\n";
myDLL->printList();


myDLL->deleteNode(2);
cout << "\nDLL after deleteNode() of last node:\n";
myDLL->printList();

/*  
    EXPECTED OUTPUT:
    ----------------
    DLL before deleteNode():
    1
    2
    3
    4
    5

    DLL after deleteNode() in middle:
    1
    2
    4
    5

    DLL after deleteNode() of first node:
    2
    4
    5

    DLL after deleteNode() of last node:
    2
    4

*/