Delete Node at Specific Position in DSA C - Practice Problems & Challenges

Challenge - 5 Problems

❓ Predict Output

intermediate

Output after deleting node at position 3

What is the printed linked list after deleting the node at position 3?

DSA C

/* Linked list: 10 -> 20 -> 30 -> 40 -> 50 -> NULL */

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

void deleteNodeAtPosition(struct Node** head_ref, int position) {
    if (*head_ref == NULL) return;
    struct Node* temp = *head_ref;
    if (position == 1) {
        *head_ref = temp->next;
        free(temp);
        return;
    }
    for (int i = 1; temp != NULL && i < position - 1; i++) {
        temp = temp->next;
    }
    if (temp == NULL || temp->next == NULL) return;
    struct Node* next = temp->next->next;
    free(temp->next);
    temp->next = next;
}

void printList(struct Node* node) {
    while (node != NULL) {
        printf("%d -> ", node->data);
        node = node->next;
    }
    printf("NULL\n");
}

int main() {
    struct Node* head = malloc(sizeof(struct Node));
    head->data = 10;
    head->next = malloc(sizeof(struct Node));
    head->next->data = 20;
    head->next->next = malloc(sizeof(struct Node));
    head->next->next->data = 30;
    head->next->next->next = malloc(sizeof(struct Node));
    head->next->next->next->data = 40;
    head->next->next->next->next = malloc(sizeof(struct Node));
    head->next->next->next->next->data = 50;
    head->next->next->next->next->next = NULL;

    deleteNodeAtPosition(&head, 3);
    printList(head);
    return 0;
}

A 10 -> 20 -> 30 -> 40 -> NULL

B 10 -> 20 -> 30 -> 50 -> NULL

C 10 -> 20 -> 40 -> 50 -> NULL

D 20 -> 30 -> 40 -> 50 -> NULL

💡 Hint

Remember that deleting at position 3 removes the third node from the list.

The node at position 3 has the value 30. After deleting it, the list links 20 directly to 40, so the list becomes 10 -> 20 -> 40 -> 50 -> NULL.

❓ Predict Output

intermediate

Output after deleting node at position 1 (head)

What is the printed linked list after deleting the node at position 1 (the head)?

DSA C

/* Linked list: 5 -> 15 -> 25 -> 35 -> NULL */

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

void deleteNodeAtPosition(struct Node** head_ref, int position) {
    if (*head_ref == NULL) return;
    struct Node* temp = *head_ref;
    if (position == 1) {
        *head_ref = temp->next;
        free(temp);
        return;
    }
    for (int i = 1; temp != NULL && i < position - 1; i++) {
        temp = temp->next;
    }
    if (temp == NULL || temp->next == NULL) return;
    struct Node* next = temp->next->next;
    free(temp->next);
    temp->next = next;
}

void printList(struct Node* node) {
    while (node != NULL) {
        printf("%d -> ", node->data);
        node = node->next;
    }
    printf("NULL\n");
}

int main() {
    struct Node* head = malloc(sizeof(struct Node));
    head->data = 5;
    head->next = malloc(sizeof(struct Node));
    head->next->data = 15;
    head->next->next = malloc(sizeof(struct Node));
    head->next->next->data = 25;
    head->next->next->next = malloc(sizeof(struct Node));
    head->next->next->next->data = 35;
    head->next->next->next->next = NULL;

    deleteNodeAtPosition(&head, 1);
    printList(head);
    return 0;
}

A NULL

B 5 -> 25 -> 35 -> NULL

C 5 -> 15 -> 35 -> NULL

D 15 -> 25 -> 35 -> NULL

💡 Hint

Deleting position 1 removes the head node.

Deleting the head node (value 5) moves the head pointer to the next node (value 15). The list becomes 15 -> 25 -> 35 -> NULL.

🔧 Debug

advanced

Identify the error in deleteNodeAtPosition function

What error will occur when running this code if position is greater than the length of the list?

DSA C

void deleteNodeAtPosition(struct Node** head_ref, int position) {
    if (*head_ref == NULL) return;
    struct Node* temp = *head_ref;
    if (position == 1) {
        *head_ref = temp->next;
        free(temp);
        return;
    }
    for (int i = 1; i < position - 1; i++) {
        temp = temp->next;
    }
    struct Node* next = temp->next->next;
    free(temp->next);
    temp->next = next;
}

A Compilation error due to missing semicolon

B Segmentation fault due to dereferencing NULL pointer

C Memory leak due to not freeing nodes

D No error, deletion works fine

💡 Hint

Consider what happens if temp or temp->next is NULL before accessing temp->next->next.

If position is greater than the list length, temp or temp->next becomes NULL. Accessing temp->next->next causes a segmentation fault (crash).

❓ Predict Output

advanced

Output after deleting node at last position

What is the printed linked list after deleting the node at the last position (position 4)?

DSA C

/* Linked list: 1 -> 2 -> 3 -> 4 -> NULL */

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

void deleteNodeAtPosition(struct Node** head_ref, int position) {
    if (*head_ref == NULL) return;
    struct Node* temp = *head_ref;
    if (position == 1) {
        *head_ref = temp->next;
        free(temp);
        return;
    }
    for (int i = 1; temp != NULL && i < position - 1; i++) {
        temp = temp->next;
    }
    if (temp == NULL || temp->next == NULL) return;
    struct Node* next = temp->next->next;
    free(temp->next);
    temp->next = next;
}

void printList(struct Node* node) {
    while (node != NULL) {
        printf("%d -> ", node->data);
        node = node->next;
    }
    printf("NULL\n");
}

int main() {
    struct Node* head = malloc(sizeof(struct Node));
    head->data = 1;
    head->next = malloc(sizeof(struct Node));
    head->next->data = 2;
    head->next->next = malloc(sizeof(struct Node));
    head->next->next->data = 3;
    head->next->next->next = malloc(sizeof(struct Node));
    head->next->next->next->data = 4;
    head->next->next->next->next = NULL;

    deleteNodeAtPosition(&head, 4);
    printList(head);
    return 0;
}

A 1 -> 2 -> 3 -> NULL

B 1 -> 2 -> 4 -> NULL

C 2 -> 3 -> 4 -> NULL

D 1 -> 3 -> 4 -> NULL

💡 Hint

Deleting the last node removes the tail of the list.

The node at position 4 has value 4. After deletion, the list ends at node with value 3, so the list is 1 -> 2 -> 3 -> NULL.

🧠 Conceptual

expert

Time complexity of deleting node at specific position in singly linked list

What is the time complexity of deleting a node at a specific position in a singly linked list of size n?

A O(n) because traversal to the node is required before deletion

B O(1) because deletion is direct with pointer adjustment

C O(log n) because of binary search to find the node

D O(n^2) because each deletion requires scanning the entire list

💡 Hint

Consider how you find the node before deleting it in a singly linked list.

To delete a node at a specific position, you must traverse the list up to that position, which takes O(n) time. Deletion itself is O(1) once the node is found.