dsa5 min read
Linked Lists — Complete Guide: All Patterns & Problem Index
Master every linked list pattern: reverse, two pointers, cycle detection, merge, clone, and design problems — with templates and full index of 45 problems.
Read →
Linked-list
49 articles
dsa2 min read
Reverse Linked List — Iterative and Recursive
Reverse a singly linked list iteratively with three-pointer technique and recursively with call stack.
Read →
dsa1 min read
Middle of the Linked List — Fast and Slow Pointers
Find the middle node of a linked list in one pass using the slow/fast pointer technique.
Read →
dsa1 min read
Linked List Cycle — Floyds Tortoise and Hare
Detect a cycle in a linked list in O(1) space using Floyd's two-pointer tortoise and hare algorithm.
Read →
dsa2 min read
Merge Two Sorted Lists — Dummy Head Merge
Merge two sorted linked lists into one sorted list using a dummy head node to simplify pointer management.
Read →
dsa1 min read
Palindrome Linked List — Split, Reverse, Compare
Check if a linked list is a palindrome by finding the middle, reversing the second half, then comparing.
Read →
dsa1 min read
Remove Duplicates from Sorted List — Single Pass
Remove duplicate nodes from a sorted linked list in O(n) with a single pointer walk.
Read →
dsa1 min read
Delete Node in a Linked List — Copy Next Value
Delete a node given only access to that node by copying the next node value and skipping the next node.
Read →
dsa1 min read
Intersection of Two Linked Lists — Two Pointer Length Trick
Find the intersection node of two linked lists in O(n) O(1) by switching pointers at the end of each list.
Read →
dsa1 min read
Convert Binary Number in Linked List to Integer — Bit Shift
Convert a linked list representing a binary number to its integer value using left-shift accumulation.
Read →
dsa1 min read
Remove Linked List Elements — Dummy Head
Remove all nodes with a given value from a linked list using a dummy head to handle edge cases cleanly.
Read →
dsa1 min read
Remove Nth Node From End of List — Fast/Slow with Dummy
Remove the nth node from the end in one pass using two pointers offset by n steps and a dummy head.
Read →
dsa1 min read
Swap Nodes in Pairs — In-Place Pointer Rewiring
Swap every two adjacent nodes in a linked list without modifying node values using pointer rewiring.
Read →
dsa1 min read
Odd Even Linked List — Two Chain In-Place
Group all odd-indexed nodes before even-indexed nodes in O(n) time and O(1) space using two pointer chains.
Read →
dsa2 min read
Rotate List — Find Length and Reconnect
Rotate a linked list to the right by k places by finding length, computing effective rotation, and rewiring.
Read →
dsa1 min read
Reorder List — Split, Reverse, Merge
Reorder a linked list into L0→Ln→L1→Ln-1 pattern by splitting at middle, reversing second half, then merging.
Read →
dsa1 min read
Add Two Numbers — Simulate Carry with Dummy Head
Add two numbers represented as reversed linked lists by simulating digit addition with carry propagation.
Read →
dsa2 min read
Add Two Numbers II — Stack to Handle Forward Order
Add two numbers given in forward order by pushing digits to stacks, then building the result list in reverse.
Read →
dsa1 min read
Partition List — Two Dummy Head Chains
Partition a linked list around value x into less-than and greater-than-or-equal chains, then join them.
Read →
dsa2 min read
Sort List — Top-Down Merge Sort
Sort a linked list in O(n log n) time and O(log n) space using top-down merge sort with fast/slow split.
Read →
dsa1 min read
Remove All Duplicates from Sorted List II — Dummy + Skip
Remove all nodes that have duplicate numbers from a sorted linked list using a dummy head and skip logic.
Read →
dsa2 min read
Copy List with Random Pointer — HashMap or Interleave
Deep copy a linked list with random pointers using either a hash map or the O(1) space interleave technique.
Read →
dsa2 min read
Flatten Multilevel Doubly Linked List — DFS Stack
Flatten a multilevel doubly linked list by inserting child sub-lists inline using DFS or an explicit stack.
Read →
dsa2 min read
Linked List Cycle II — Floyd's Cycle Start Detection
Find the node where a cycle begins using Floyd's algorithm: detect meeting point, then reset one pointer to head.
Read →
dsa1 min read
Find the Duplicate Number — Floyd's on Array as Linked List
Find the duplicate in an array of n+1 integers in O(1) space by treating indices as a linked list with Floyd's cycle detection.
Read →
dsa1 min read
Next Greater Node in Linked List — Monotonic Stack
Find the next greater value for each node in a linked list using a monotonic decreasing stack of indices.
Read →
dsa1 min read
Design Linked List — Sentinel Doubly Linked List
Implement a doubly linked list with sentinel head and tail nodes for clean O(1) insertions and deletions.
Read →
dsa1 min read
Swapping Nodes in a Linked List — Find Kth from Front and Back
Swap the kth node from the front with the kth node from the end by finding both with two pointers.
Read →
dsa1 min read
Remove Zero Sum Consecutive Nodes — Prefix Sum Map
Remove consecutive nodes that sum to zero by tracking prefix sums in a map and relinking past zero-sum runs.
Read →
dsa2 min read
Split Linked List in Parts — Even Distribution
Split a linked list into k consecutive parts as evenly as possible, front parts get the extra nodes.
Read →
dsa2 min read
Reverse Linked List II — In-Place Partial Reversal
Reverse the portion of a linked list between positions left and right in one pass using careful pointer manipulation.
Read →
dsa2 min read
Maximum Twin Sum of a Linked List — Split and Reverse
Find the maximum sum of twin nodes (node i + node n-1-i) by reversing the second half and comparing pairs.
Read →
dsa1 min read
Merge Nodes In Between Zeros — Pointer Walk
Merge all nodes between 0s into a single node with their sum, modifying the list in-place.
Read →
dsa1 min read
Delete the Middle Node — Fast/Slow with Prev Pointer
Delete the middle node of a linked list using a prev-pointer variant of the fast/slow technique.
Read →
dsa2 min read
Reverse Nodes in Even-Length Groups — Group Counting
Reverse nodes in each even-length group of a linked list by counting group sizes and selectively reversing.
Read →
dsa2 min read
Insert into a Sorted Circular List — Pointer Scan
Insert a value into a sorted circular linked list by finding the correct position with careful edge case handling.
Read →
dsa1 min read
Linked List Components — HashSet Membership Check
Count the number of connected components of a linked list that consist of nodes in a given set.
Read →
dsa2 min read
Flatten Binary Tree to Linked List — Morris Traversal
Flatten a binary tree in-place into a linked list following pre-order using the Morris traversal approach.
Read →
dsa1 min read
Convert Sorted List to BST — Fast/Slow + Recursion
Convert a sorted linked list to a height-balanced BST by repeatedly finding the middle node as root.
Read →
dsa2 min read
Reverse Nodes in k-Group — Recursive Group Reversal
Reverse every k nodes of a linked list recursively: check k nodes exist, reverse them, recurse on the rest.
Read →
dsa2 min read
Merge K Sorted Lists — Min-Heap or Divide and Conquer
Merge k sorted linked lists into one sorted list using a min-heap for O(n log k) time complexity.
Read →
dsa2 min read
Sort List Bottom-Up — O(1) Space Merge Sort
Sort a linked list in O(n log n) time and O(1) space using bottom-up merge sort with doubling sublist sizes.
Read →
dsa2 min read
Convert Sorted List to BST — In-Order O(n) Build
Build a balanced BST from a sorted list in O(n) by counting nodes, building in-order, and consuming list nodes.
Read →
dsa2 min read
LRU Cache — Doubly Linked List + HashMap Implementation
Implement LRU Cache from scratch using a doubly linked list with sentinel nodes and a hash map for O(1) operations.
Read →
dsa2 min read
Design Browser History — Doubly Linked List Implementation
Design a browser history with visit, back, and forward operations using a doubly linked list for O(1) navigation.
Read →
dsa5 min read
Linked Lists Master Recap — All Patterns & Templates
Complete cheatsheet for Linked Lists: all 7 patterns, template code, Big O reference, and MAANG interview priority guide.
Read →
dsa2 min read
Amazon — Merge K Sorted Lists (Min-Heap)
Merge k sorted linked lists into one sorted list using a min-heap. O(n log k) time by always extracting the current minimum across all list heads.
Read →
dsa4 min read
LRU Cache — Design with O(1) Get and Put
Implement an LRU (Least Recently Used) cache with O(1) get and put using a doubly linked list and hashmap. Full 5-language solutions.
Read →
dsa4 min read
LFU Cache — O(1) Least Frequently Used Eviction
Implement an LFU cache with O(1) get and put. Uses two hashmaps and per-frequency doubly linked lists to track access frequency and recency simultaneously.
Read →