Linked list 3

3.a
#include 
#include 

struct Node {
    int data;
    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->next = NULL;
    return newNode;
}

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

void insertAfter(struct Node* head, int key, int data) {
    if (head == NULL) return;
    
    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;
    current->next = newNode;
}

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

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

void deleteByKey(struct Node** head, int key) {
    struct Node *temp = *head, *prev = NULL;

    if (temp != NULL && temp->data == key) {
        *head = temp->next;
        free(temp);
        return;
    }

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

    if (temp == NULL) return;

    prev->next = temp->next;
    free(temp);
}

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

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

    insertAfter(head, 10, 20);
    traverseList(head);

    deleteBeginning(&head);
    traverseList(head);

    deleteEnd(&head);
    traverseList(head);

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

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

    return 0;
}

3.b
#include 
#include 

struct Node {
    int data;
    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->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;
}

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

int searchList(struct Node* head, int key) {
    struct Node* current = head;
    int position = 1;
    while (current != NULL) {
        if (current->data == key) {
            return position;
        }
        current = current->next;
        position++;
    }
    return -1;
}

int main() {
    struct Node* head = NULL;
    int searchKey = 30;
    int position;

    insertEnd(&head, 10);
    insertEnd(&head, 20);
    insertEnd(&head, 30);
    insertEnd(&head, 40);
    insertEnd(&head, 50);

    traverseList(head);

    position = searchList(head, searchKey);

    if (position != -1) {
        printf("Element %d found at position %d.\n", searchKey, position);
    } else {
        printf("Element %d not found.\n", searchKey);
    }
    
    searchKey = 99;
    position = searchList(head, searchKey);
    if (position != -1) {
        printf("Element %d found at position %d.\n", searchKey, position);
    } else {
        printf("Element %d not found.\n", searchKey);
    }

    return 0;
}