WBJECA 2025 — Computer PYQ

Correct Option: (D) $O(1)$

Explanation

In a singly linked list, the time complexity of deleting a node depends on which node is being deleted.

• Best Case ($O(1)$): The best case occurs when you want to delete the head node of the linked list. Since you already have a direct pointer (or reference) to the head of the list, you can simply update the head pointer to point to the second node in the list:

  $$Hea{d}_{new}=Hea{d}_{old}\to next$$

  This operation takes constant time, as no traversal is required.

• Worst Case ($O(n)$): The worst case occurs when you need to delete a node at the end of the list or a specific node by its value. Because a singly linked list only has forward pointers, you must traverse the list from the beginning to find the node and its previous node, leading to a linear time complexity:

  $$Time\approx O(n)$$