Linked list 5

5a
#include 
#include 

struct Node {
    int data;
    struct Node* prev;
    struct Node* next;
};

struct Node* createNode(int data) {
    struct Node* newNode = (struct Node*)malloc(sizeof(struct Node));
    if (newNode == NULL) return NULL;
    newNode->data = data;
    newNode->prev = NULL;
    newNode->next = NULL;
    return newNode;
}

void traverseForward(struct Node* head) {
    struct Node* current = head;
    if (head == NULL) {
        printf("List Empty.\n");
        return;
    }
    printf("Forward: NULL <-> ");
    while (current != NULL) {
        printf("%d <-> ", current->data);
        current = current->next;
    }
    printf("NULL\n");
}

void insertBeginning(struct Node** head, int data) {
    struct Node* newNode = createNode(data);
    if (newNode == NULL) return;
    newNode->next = *head;
    if (*head != NULL) {
        (*head)->prev = newNode;
    }
    *head = newNode;
}

void insertEnd(struct Node** head, int data) {
    struct Node* newNode = createNode(data);
    if (newNode == NULL) return;
    if (*head == NULL) {
        *head = newNode;
        return;
    }
    struct Node* last = *head;
    while (last->next != NULL) {
        last = last->next;
    }
    last->next = newNode;
    newNode->prev = last;
}

void insertAfter(struct Node* head, int key, int data) {
    struct Node* current = head;
    while (current != NULL && current->data != key) {
        current = current->next;
    }

    if (current == NULL) return;

    struct Node* newNode = createNode(data);
    if (newNode == NULL) return;

    newNode->next = current->next;
    newNode->prev = current;
    if (current->next != NULL) {
        current->next->prev = newNode;
    }
    current->next = newNode;
}

void deleteBeginning(struct Node** head) {
    if (*head == NULL) return;
    struct Node* temp = *head;
    *head = (*head)->next;
    if (*head != NULL) {
        (*head)->prev = NULL;
    }
    free(temp);
}

void deleteEnd(struct Node** head) {
    if (*head == NULL) return;
    struct Node* temp = *head;
    if (temp->next == NULL) {
        free(*head);
        *head = NULL;
        return;
    }
    while (temp->next != NULL) {
        temp = temp->next;
    }
    temp->prev->next = NULL;
    free(temp);
}

void deleteByKey(struct Node** head, int key) {
    struct Node* current = *head;

    while (current != NULL && current->data != key) {
        current = current->next;
    }

    if (current == NULL) return;

    if (current->prev != NULL) {
        current->prev->next = current->next;
    } else {
        *head = current->next;
    }

    if (current->next != NULL) {
        current->next->prev = current->prev;
    }

    free(current);
}

int main() {
    struct Node* head = NULL;

    insertEnd(&head, 10);
    insertBeginning(&head, 5);
    insertEnd(&head, 30);
    traverseForward(head);

    insertAfter(head, 5, 7);
    traverseForward(head);

    deleteBeginning(&head);
    traverseForward(head);

    deleteEnd(&head);
    traverseForward(head);

    insertEnd(&head, 40);
    insertEnd(&head, 50);
    traverseForward(head);

    deleteByKey(&head, 40);
    traverseForward(head);

    return 0;
}

5b
#include 
#include 

struct Node {
    int data;
    struct Node* prev;
    struct Node* next;
};

struct Node* createNode(int data) {
    struct Node* newNode = (struct Node*)malloc(sizeof(struct Node));
    if (newNode == NULL) return NULL;
    newNode->data = data;
    newNode->prev = NULL;
    newNode->next = NULL;
    return newNode;
}

void insertEnd(struct Node** head, int data) {
    struct Node* newNode = createNode(data);
    if (newNode == NULL) return;
    if (*head == NULL) {
        *head = newNode;
        return;
    }
    struct Node* last = *head;
    while (last->next != NULL) {
        last = last->next;
    }
    last->next = newNode;
    newNode->prev = last;
}

void traverseForward(struct Node* head) {
    struct Node* current = head;
    if (head == NULL) {
        printf("List Empty.\n");
        return;
    }
    printf("Forward: NULL <-> ");
    while (current != NULL) {
        printf("%d <-> ", current->data);
        current = current->next;
    }
    printf("NULL\n");
}

void traverseReverse(struct Node* head) {
    struct Node* current = head;
    if (head == NULL) {
        printf("List Empty.\n");
        return;
    }

    while (current->next != NULL) {
        current = current->next;
    }

    printf("Reverse: NULL <-> ");
    while (current != NULL) {
        printf("%d <-> ", current->data);
        current = current->prev;
    }
    printf("NULL\n");
}

int main() {
    struct Node* head = NULL;

    insertEnd(&head, 10);
    insertEnd(&head, 20);
    insertEnd(&head, 30);
    insertEnd(&head, 40);

    traverseForward(head);
    traverseReverse(head);

    return 0;
}