Delete Node at Specific Position in DSA Rust - Interactive Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to create a new node with the given value.

DSA Rust

let new_node = Box::new(Node { data: [1], next: None });

Drag options to blanks, or click blank then click option'

Avalue

Bnext

Chead

DNone

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'next' instead of the value for the data field.

Using 'head' which is a pointer, not the value.

We create a new node with the data field set to the given value.

2fill in blank

medium

Complete the code to check if the position to delete is the head (position 0).

DSA Rust

if position == [1] {

Drag options to blanks, or click blank then click option'

ANone

B1

C-1

D0

Attempts:

3 left

💡 Hint

Common Mistakes

Checking for position == 1 instead of 0.

Using None which is not a number.

Position 0 means the head node should be deleted.

3fill in blank

hard

Fix the error in the loop condition to traverse to the node before the one to delete.

DSA Rust

for _ in 0..([1] - 1) { current = current.next.as_mut().unwrap(); }

Drag options to blanks, or click blank then click option'

Aposition - 1

Bposition + 1

Cposition * 2

Dposition

Attempts:

3 left

💡 Hint

Common Mistakes

Using position + 1 causes out-of-bounds traversal.

Using position - 1 inside the range causes incorrect loop count.

We loop from 0 to position - 1 to reach the node before the target.

4fill in blank

hard

Fill both blanks to correctly update the next pointer to skip the deleted node.

DSA Rust

let next_node = current.next.as_mut().unwrap().next.take();
current.next = [1];

Drag options to blanks, or click blank then click option'

Acurrent.next

Bnext_node

CNone

DSome(Box::new(Node { data: 0, next: None }))

Attempts:

3 left

💡 Hint

Common Mistakes

Assigning current.next to None removes all nodes after current.

Assigning current.next to current.next causes no change.

We assign current.next to next_node to remove the target node from the list.

5fill in blank

hard

Fill all three blanks to complete the function that deletes a node at a given position.

DSA Rust

pub fn delete_at_position(mut head: Option<Box<Node>>, position: usize) -> Option<Box<Node>> {
    if position == [1] {
        return head.and_then(|node| node.next);
    }
    let mut current = head.as_mut().unwrap();
    for _ in 0..([2] - 1) {
        current = current.next.as_mut().unwrap();
    }
    let next_node = current.next.as_mut().unwrap().next.take();
    current.next = [3];
    head
}

Drag options to blanks, or click blank then click option'

A0

Bposition

Cnext_node

DNone

Attempts:

3 left

💡 Hint

Common Mistakes

Not handling deletion of head node separately.

Incorrect loop range causing panic.

Assigning current.next incorrectly.

Position 0 means delete head; loop to position - 1; update current.next to skip deleted node.

Practice

1. What does deleting a node at a specific position in a linked list mean?

easy

A. Removing the node located at that position and linking its neighbors

B. Adding a new node at that position

C. Swapping two nodes in the list

D. Counting the number of nodes up to that position

Solution

1. Step 1: Understand node deletion

   Deleting a node means removing it from the list and connecting the previous node to the next node.

2. Step 2: Apply to specific position

   At a specific position, the node at that index is removed and neighbors are linked to maintain the list.

3. Final Answer:

   Removing the node located at that position and linking its neighbors -> Option A

4. Quick Check:

   Delete node = Remove and link neighbors [OK]

Hint: Delete means remove node and link neighbors [OK]

Common Mistakes:

• Confusing deletion with insertion
• Thinking deletion swaps nodes
• Ignoring neighbor linking after deletion

2. Which Rust syntax correctly declares a mutable linked list node struct?

easy

A. struct Node { data: i32, mut next: Option }

B. struct Node { data: i32, next: Option }

C. struct Node { data: i32, next: Box<Node> }

D. struct Node { data: i32, next: &Node }

Solution

1. Step 1: Check struct fields

   Rust linked list nodes use Option for next to allow null and ownership.

2. Step 2: Validate mutability

   Mutability is controlled outside struct fields; 'mut' keyword inside struct is invalid.

3. Final Answer:

   struct Node { data: i32, next: Option } -> Option B

4. Quick Check:

   Option for next pointer [OK]

Hint: Use Option for next pointer [OK]

Common Mistakes:

• Adding 'mut' inside struct fields
• Using Box<Node> without Option causing no null
• Using references (&Node) causing lifetime issues

3. What is the output linked list after deleting the node at position 2 (0-based) from this list: 10 -> 20 -> 30 -> 40 -> null?

fn main() {
    let mut head = Some(Box::new(Node { data: 10, next: Some(Box::new(Node { data: 20, next: Some(Box::new(Node { data: 30, next: Some(Box::new(Node { data: 40, next: None })) })) })) }));
    delete_at_position(&mut head, 2);
    print_list(&head);
}

fn delete_at_position(head: &mut Option, pos: usize) {
    if pos == 0 {
        *head = head.as_mut().and_then(|node| node.next.take());
        return;
    }
    let mut current = head.as_mut();
    for _ in 0..pos-1 {
        if let Some(node) = current {
            current = node.next.as_mut();
        }
    }
    if let Some(node) = current {
        node.next = node.next.as_mut().and_then(|next_node| next_node.next.take());
    }
}

fn print_list(head: &Option) {
    let mut current = head;
    while let Some(node) = current {
        print!("{} -> ", node.data);
        current = &node.next;
    }
    println!("null");
}

struct Node {
    data: i32,
    next: Option,
}

medium

A. 10 -> 20 -> 30 -> null

B. 10 -> 30 -> 40 -> null

C. 10 -> 20 -> 40 -> null

D. 20 -> 30 -> 40 -> null

Solution

1. Step 1: Identify node to delete at position 2

   Position 2 node has data 30 in list 10 -> 20 -> 30 -> 40 -> null.

2. Step 2: Remove node 30 and link 20 to 40

   After deletion, list becomes 10 -> 20 -> 40 -> null.

3. Final Answer:

   10 -> 20 -> 40 -> null -> Option C

4. Quick Check:

   Deleted node 30 at pos 2 [OK]

Hint: Delete node at pos links previous to next [OK]

Common Mistakes:

• Deleting wrong node index
• Not linking neighbors correctly
• Confusing 0-based and 1-based positions

4. Identify the bug in this Rust function that deletes a node at a given position in a linked list:

fn delete_at_position(head: &mut Option, pos: usize) {
    let mut current = head.as_mut();
    for _ in 0..pos {
        if let Some(node) = current {
            current = node.next.as_mut();
        }
    }
    if let Some(node) = current {
        node.next = node.next.as_mut().and_then(|next_node| next_node.next.take());
    }
}

medium

A. All of the above

B. Loop runs one time too many, skipping the previous node

C. Does not update head pointer when deleting first node

D. Function does not handle deleting head node (pos 0)

Solution

1. Step 1: Analyze loop range for traversal

   The loop runs from 0 to pos, moving current to node at pos, not previous node needed for deletion.

2. Step 2: Check head deletion handling

   Function does not handle pos 0 case, so head pointer is never updated if first node is deleted.

3. Step 3: Summarize all issues

   Loop skips previous node, no head update on pos 0, so all listed bugs exist.

4. Final Answer:

   All of the above -> Option A

5. Quick Check:

   Loop and head update bugs = All above [OK]

Hint: Check loop range and head update for deletion [OK]

Common Mistakes:

• Looping to node instead of previous node
• Ignoring deletion of head node
• Not updating head pointer on deletion

5. Given a singly linked list with nodes: 5 -> 15 -> 25 -> 35 -> 45 -> null, write a Rust function to delete the node at position 3 (0-based). What will be the final list after deletion? Choose the correct final list output.

medium

A. 5 -> 15 -> 35 -> 45 -> null

B. 5 -> 15 -> 25 -> 35 -> null

C. 15 -> 25 -> 35 -> 45 -> null

D. 5 -> 15 -> 25 -> 45 -> null

Solution

1. Step 1: Identify node at position 3

   Position 3 node has value 35 in list 5 -> 15 -> 25 -> 35 -> 45 -> null.

2. Step 2: Delete node 35 and link 25 to 45

   After deletion, list becomes 5 -> 15 -> 25 -> 45 -> null.

3. Final Answer:

   5 -> 15 -> 25 -> 45 -> null -> Option D

4. Quick Check:

   Deleted node 35 at pos 3 [OK]

Hint: Delete node at pos and link neighbors [OK]

Common Mistakes:

• Deleting wrong position node
• Not linking previous node to next
• Confusing 0-based indexing