#linked lists

22 linked lists interview questions, asked at Meta, Google, Microsoft and 8 more companies. Last asked Oct 2026.

Follow one-way links to the endpoint or the last node before a loopCodingA network has nodes joined by one-way links, and each node links to at most one other node. Starting from a given node, follow the links and return the endpoint: the last node the…
Last asked Oct 2026
Streaming top-K frequent elements with O(1) updatesCodingElements arrive one at a time from an unbounded stream. Design a structure that can report, at any moment, the K elements seen most often so far. Clarify what K is and whether it…
Last asked Sep 2026
Flatten a linked list with side branches into one doubly linked listCodingEach node of a singly linked list has a forward link and may also have one side branch: a link to the head of another list, whose nodes may have side branches of their own…
Last asked Sep 2026
Linked-list queue with deletionsCodingImplement a queue on a linked list with enqueue and dequeue, then extend it through follow-ups that delete elements from the queue.
Last asked Sep 2026
+2
Copy list with random pointerCodingEach node of a singly linked list has a next pointer and a random pointer that may point to any node in the list or to nothing. Return a deep copy of the list in which no pointer…
Last asked Aug 2026
Detect and break a cycle in a linked listCodingDecide whether a singly linked list has a cycle, find the node where the cycle begins, and break the cycle so the list ends.
Last asked Jun 2026
+1
Copy a linked list with random pointersCodingEach node of a linked list has a next pointer and a random pointer that can point at any node or nowhere. Make a deep copy of the list. Do it with a map from old nodes to new…
Last asked Jun 2026
+1
Convert a BST to a sorted circular doubly linked listCodingRearrange a binary search tree in place into a circular doubly linked list in sorted order, reusing the left and right pointers as previous and next. Do an in-order traversal that…
Last asked Jun 2026
Palindrome linked list without modifying the listCodingDecide whether a singly linked list reads the same both ways. Do it without changing the list, or restore it exactly if you reverse part of it. Compare the stack approach with…
Last asked Apr 2026
Merge k sorted listsCodingMerge k sorted linked lists into one sorted list. Compare a min-heap of list heads with pairwise merging, and give the time complexity in terms of the total number of nodes and k.
Last asked Feb 2026
Editable sequence with a markerCodingDesign a sequence of elements with a marker on one of them. Support adding or removing a run of elements at a position, moving a run from one position to another, and setting a…
Last asked Feb 2026
Populate next right pointers in each nodeCodingEach node of a binary tree (not necessarily perfect) has a next pointer. Set every node's next to the node to its right on the same level, or null at the end of a level…
Last asked Feb 2026
Intersection of two linked lists that may have cyclesCodingGiven the heads of two singly linked lists, each of which may or may not contain a cycle, decide whether they share a node and return the first shared node. Find where each list's…
Last asked Jan 2026
Insert into a sorted circular linked listCodingYou are given a node somewhere in a circular linked list sorted in ascending order. Insert a value so the list stays sorted and return a node of the list. Handle an empty list, a…
Last asked Dec 2025
Add two big integers stored as digit listsCodingTwo non-negative integers too large for built-in types are given as lists of digits. Return their sum in the same form. Handle different lengths and the final carry, and say how…
Last asked Nov 2025
Reverse nodes in k-groupCodingReverse a linked list in groups of k nodes, leaving a final group shorter than k as it is. Do it in place with O(1) extra space.
Last asked Oct 2025
Reverse a linked list between nodes with equal valuesCodingIn a singly linked list, whenever two nodes hold the same value, reverse the part of the list between them. Clarify with the interviewer which pairs count and whether the matching…
Last asked Sep 2025
LRU cache where each item counts by its quantityCodingImplement an LRU cache in which every item carries a quantity, and capacity is measured in total quantity rather than number of items. A put may evict several least recently used…
Last asked Aug 2025
Nth node from the end of a linked listCodingReturn (or remove) the n-th node from the end of a singly linked list in one pass, moving a lead pointer n steps ahead of a trailing one.
Last asked Aug 2025
LFU cacheCodingImplement a least-frequently-used cache with get and put in O(1). When full, evict the key used least often, breaking ties by least recently used. Keep a map from key to node and…
Last asked Jul 2025
Compare two linked lists of string chunksCodingTwo singly linked lists each hold pieces of text, one piece per node (in the reported version, one character per node stored as a string). Decide whether both lists spell the same…
Last asked Jul 2025
+1
Merge two sorted linked listsCodingMerge two sorted linked lists into one sorted list and return its head, reusing the existing nodes. Do it iteratively with a dummy head, then discuss the recursive version.
Last asked Jul 2025