All patterns
22 patterns in study order. Each one has a guide that opens with the copy-paste skeleton, then the problems that drill it.
Foundations
Big O, arrays, Java collections tips and tree fundamentals.
6 pages
Two Pointers
Sorted arrays and pair/triplet search.
6 pages
Cyclic Sort
Problems over a fixed 1..N range.
4 pages
BFS
Tree levels and shortest path on unweighted graphs.
6 pages
Backtracking & Subsets
Combinations, permutations and subsets.
5 pages
Binary Search (Modified)
Searching a sorted or monotonic answer space.
6 pages
Dynamic Programming
Optimisation over overlapping subproblems.
Pattern guide → Pattern 14: Dynamic Programming (Memoization vs. Tabulation)
8 pages
Blind 75
The curated 75-problem interview list, grouped by category.
Pattern guide → Blind 75 — Array Pattern Guide
- LC 133Clone GraphMedium
- LC 208Implement Trie (Prefix Tree)Medium
- LC 3Longest Substring Without Repeating CharactersMedium
- LC 104Maximum Depth of Binary TreeEasy
- LC 56Merge IntervalsMedium
- LC 23Merge k Sorted ListsHard
- LC 206Reverse Linked ListEasy
- LC 73Set Matrix ZeroesMedium
- LC 371Sum of Two IntegersMedium
- LC 1Two SumEasy
- LC 139Word BreakMedium
- LC 124Binary Tree Maximum Path SumHard
- LC 377Combination Sum IVMedium
- LC 207Course ScheduleMedium
- LC 211Design Add and Search Words Data StructureMedium
- LC 141Linked List CycleEasy
- LC 424Longest Repeating Character ReplacementMedium
- LC 53Maximum SubarrayMedium
- LC 435Non-overlapping IntervalsMedium
- LC 191Number of 1 BitsEasy
- LC 54Spiral MatrixMedium
- LC 347Top K Frequent ElementsMedium
- LC 102Binary Tree Level Order TraversalMedium
- LC 338Counting BitsEasy
- LC 295Find Median from Data StreamHard
- LC 198House RobberMedium
- LC 57Insert IntervalMedium
- LC 152Maximum Product SubarrayMedium
- LC 76Minimum Window SubstringHard
- LC 417Pacific Atlantic Water FlowMedium
- LC 19Remove Nth Node From End of ListMedium
- LC 48Rotate ImageMedium
- LC 212Word Search IIHard
- LC 271Encode and Decode StringsMedium
- LC 153Find Minimum in Rotated Sorted ArrayMedium
- LC 213House Robber IIMedium
- LC 253Meeting Rooms IIMedium
- LC 268Missing NumberEasy
- LC 200Number of IslandsMedium
- LC 143Reorder ListMedium
- LC 297Serialize and Deserialize Binary TreeHard
- LC 79Word SearchMedium
- LC 91Decode WaysMedium
- LC 49Group AnagramsMedium
- LC 128Longest Consecutive SequenceMedium
- LC 21Merge Two Sorted ListsEasy
- LC 190Reverse BitsEasy
- LC 33Search in Rotated Sorted ArrayMedium
- LC 572Subtree of Another TreeEasy
- LC 153SumMedium
- LC 105Construct Binary Tree from Preorder and Inorder TraversalMedium
- LC 261Graph Valid TreeMedium
- LC 55Jump GameMedium
- LC 23Merge K Sorted ListsHard
- LC 20Valid ParenthesesEasy
- LC 11Container With Most WaterMedium
- LC 1143Longest Common SubsequenceMedium
- LC 5Longest Palindromic SubstringMedium
- LC 323Number of Connected Components in an Undirected GraphMedium
- LC 98Validate Binary Search TreeMedium
- LC 269Alien DictionaryHard
- LC 121Best Time to Buy and Sell StockEasy
- LC 70Climbing StairsEasy
- LC 230Kth Smallest Element in a BSTMedium
- LC 647Palindromic SubstringsMedium
- LC 322Coin ChangeMedium
- LC 217Contains DuplicateEasy
- LC 235Lowest Common Ancestor of a Binary Search TreeMedium
- LC 242Valid AnagramEasy
- LC 300Longest Increasing SubsequenceMedium
- LC 238Product of Array Except SelfMedium
- LC 100Same TreeEasy
- LC 125Valid PalindromeEasy
- LC 226Invert Binary TreeEasy
- LC 62Unique PathsMedium
89 pages
Graph Patterns
BFS, DFS, topological sort, union-find, Dijkstra and Bellman-Ford.
Pattern guide → Pattern 16: Graph Patterns (BFS / DFS / Topological Sort / Union-Find / Dijkstra)
8 pages
Union-Find (DSU)
Dynamic connectivity and grouping.
Pattern guide → Pattern 17: Union-Find (Disjoint Set Union — DSU)
1 pages
1 pages
1 pages
Monotonic Stack
Next or previous greater/smaller element.
4 pages
Stacks & Queues
LIFO, FIFO, monotonic deque and design questions.
Pattern guide → Pattern 21: Stacks & Queues (incl. Monotonic Deque, Design & Simulation)
6 pages