Remove Nth Node from End of List in DSA C - Interactive Practice

Practice - 5 Tasks

1fill in blank

easy

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

DSA C

struct ListNode* newNode = (struct ListNode*)malloc(sizeof(struct ListNode));
newNode->val = [1];
newNode->next = NULL;

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Ax

Bvalue

Cn

Dval

Attempts:

3 left

💡 Hint

Common Mistakes

Using an undefined variable name like 'val' or 'value'.

Confusing the node pointer with the value variable.

The variable 'x' holds the value to assign to the new node's val field.

2fill in blank

medium

Complete the code to advance the fast pointer n steps ahead.

DSA C

for (int i = 0; i < [1]; i++) {
    fast = fast->next;
}

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Alength

Bcount

Cn

Dindex

Attempts:

3 left

💡 Hint

Common Mistakes

Using the wrong variable like length or count which are unrelated here.

Off-by-one errors in the loop condition.

We need to move the fast pointer n steps ahead, so the loop runs n times.

3fill in blank

hard

Fix the error in the condition to check if fast pointer reached the end.

DSA C

if (fast == [1]) {
    return head->next;
}

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Afast->next

BNULL

Chead

Dtail

Attempts:

3 left

💡 Hint

Common Mistakes

Checking against head or tail which are not correct here.

Using fast->next which can cause a null pointer dereference.

When fast reaches NULL, it means we need to remove the head node.

4fill in blank

hard

Fill both blanks to move fast and slow pointers until fast reaches the end.

DSA C

while (fast->next != [1]) {
    fast = fast->next;
    slow = [2];
}

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ANULL

Bslow->next

Chead

Dfast

Attempts:

3 left

💡 Hint

Common Mistakes

Using head or fast in place of slow->next.

Checking fast->next against head instead of NULL.

We move fast until fast->next is NULL, and move slow one step forward each time.

5fill in blank

hard

Fill all three blanks to remove the nth node from end by adjusting pointers.

DSA C

struct ListNode* toDelete = slow->[1];
slow->[2] = toDelete->[3];
free(toDelete);

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Anext

Bprev

Attempts:

3 left

💡 Hint

Common Mistakes

Using prev pointers which do not exist in singly linked list.

Not freeing the deleted node causing memory leaks.

We set toDelete as slow->next, then link slow->next to toDelete->next, and free toDelete.