Curated to cover ~90% of MAANG / big-MNC SDE3+ DSA rounds .
Source blend:
N = NeetCode 150B = Blind 75G = Grind 169S = Striver SDE / A2Z picksP = Sean Prashad pattern fillsH = SDE3-tier Hard (company-tagged)
Difficulty: E = Easy, M = Medium, H = Hard.
Filename convention: topics/<topic>/problems/NNN-kebab-name.md where NNN is the LeetCode number.
# Title Pattern Diff Sources 001 Two Sum Hash Map Lookup E N,B,G 049 Group Anagrams Hash Map Bucketing M N,B,G 217 Contains Duplicate Hash Set E N,B 242 Valid Anagram Hash Map Counting E N,B 347 Top K Frequent Elements Bucket Sort / Heap M N,B,G 271 Encode and Decode Strings String Encoding M N,B 238 Product of Array Except Self Prefix Suffix M N,B,G 36 Valid Sudoku Hash Set per Row/Col/Box M N 128 Longest Consecutive Sequence Hash Set Sequence M N,B,G 1 Two Sum II — sorted Two Pointers E G 167 Two Sum II — Input Sorted Two Pointers M N,G 88 Merge Sorted Array Two Pointers (in-place) E G,S 26 Remove Duplicates from Sorted Array Two Pointers E G,S 27 Remove Element Two Pointers E S 169 Majority Element Boyer-Moore E G,S 53 Maximum Subarray Kadane M N,B,G,S 152 Maximum Product Subarray DP track min/max M N,B 121 Best Time to Buy/Sell Stock One Pass Min E N,B,G 122 Best Time to Buy/Sell Stock II Greedy M G 189 Rotate Array Reverse Trick M G,S 48 Rotate Image Transpose + Reverse M N,B 54 Spiral Matrix Layered Traversal M N,B
# Title Pattern Diff Sources 125 Valid Palindrome Two Pointers E N,B,G 11 Container With Most Water Two Pointers (max area) M N,B,G 15 3Sum Sort + Two Pointers M N,B,G 16 3Sum Closest Sort + Two Pointers M S 18 4Sum Sort + Nested Two Pointers M S 42 Trapping Rain Water Two Pointers / DP H N,B,G,H 75 Sort Colors Dutch National Flag M G,S 283 Move Zeroes Two Pointers E G 392 Is Subsequence Two Pointers E P 680 Valid Palindrome II Two Pointers + Skip E P
# Title Pattern Diff Sources 3 Longest Substring Without Repeating Variable Window + Set M N,B,G 121 Best Time to Buy/Sell Stock Min-window E N,B 424 Longest Repeating Character Replacement Window + counts M N,B 567 Permutation in String Fixed Window + counts M N 76 Minimum Window Substring Variable Window + need-have H N,B,G,H 239 Sliding Window Maximum Monotonic Deque H N,B,G,H 209 Minimum Size Subarray Sum Variable Window M G,P 904 Fruit Into Baskets Window with k=2 distinct M P 1004 Max Consecutive Ones III Window with k flips M P 438 Find All Anagrams in a String Fixed Window + counts M P 30 Substring with Concatenation of All Words Fixed Window + map H P,H 992 Subarrays with K Different Integers Window AtMost(K) - AtMost(K-1) H H
# Title Pattern Diff Sources 20 Valid Parentheses Stack Match E N,B,G 155 Min Stack Stack + Min M N,B,G 150 Evaluate Reverse Polish Notation Stack M N,B 22 Generate Parentheses Backtracking + Stack M N,B,G 739 Daily Temperatures Monotonic Stack M N,B,G 853 Car Fleet Sort + Stack M N 84 Largest Rectangle in Histogram Monotonic Stack H N,B,G,H 71 Simplify Path Stack M P 232 Implement Queue using Stacks Two Stacks E P 394 Decode String Stack M P
# Title Pattern Diff Sources 704 Binary Search Vanilla E N,G 74 Search a 2D Matrix BS on flattened M N,B 875 Koko Eating Bananas BS on Answer M N,B 153 Find Min in Rotated Sorted Array BS on rotation M N,B,G 33 Search in Rotated Sorted Array BS modified M N,B,G 981 Time Based Key-Value Store BS on timestamps M N,B 4 Median of Two Sorted Arrays BS partition H N,B,G,H 35 Search Insert Position BS lower-bound E G 162 Find Peak Element BS on slope M P 410 Split Array Largest Sum BS on Answer H H,P 1011 Capacity to Ship Packages in D Days BS on Answer M P 540 Single Element in Sorted Array BS pair invariant M P
# Title Pattern Diff Sources 206 Reverse Linked List In-place reversal E N,B,G 21 Merge Two Sorted Lists Merge E N,B,G 143 Reorder List Find mid + reverse + merge M N,B 19 Remove Nth From End Two pointers M N,B,G 138 Copy List with Random Pointer Hash map / interleave M N,B 2 Add Two Numbers Linked-list arithmetic M N,B,G 141 Linked List Cycle Floyd's E N,B,G 142 Linked List Cycle II Floyd's + entry M N,G 287 Find the Duplicate Number Floyd on indices M N,B 146 LRU Cache Hash + DLL M N,B,G 23 Merge K Sorted Lists Heap / Divide H N,B,G,H 25 Reverse Nodes in K-Group In-place reversal H N,B,H 92 Reverse Linked List II In-place sublist reversal M P 234 Palindrome Linked List Mid + reverse E P
# Title Pattern Diff Sources 226 Invert Binary Tree DFS E N,B,G 104 Maximum Depth of Binary Tree DFS E N,B,G 543 Diameter of Binary Tree DP-on-tree E N,B 110 Balanced Binary Tree Post-order E N,B 100 Same Tree DFS E N,B 572 Subtree of Another Tree DFS + isSame E N,B 235 LCA of BST BST property M N,B 102 Binary Tree Level Order Traversal BFS M N,B,G 199 Binary Tree Right Side View BFS M N,B 1448 Count Good Nodes in Binary Tree DFS + max-on-path M N 98 Validate BST DFS w/ bounds M N,B,G 230 Kth Smallest in BST Inorder M N,B 105 Build Tree from Preorder + Inorder DFS M N,B,G 124 Binary Tree Maximum Path Sum DP-on-tree H N,B,G,H 297 Serialize/Deserialize Binary Tree DFS string H N,B,G,H 116 Populating Next Right Pointers BFS / O(1) space M P 437 Path Sum III Prefix sum on tree M P 113 Path Sum II Backtracking M S 236 LCA of Binary Tree DFS M G,S 257 Binary Tree Paths Backtracking E S 222 Count Complete Tree Nodes BS + heights E P 173 Binary Search Tree Iterator Stack inorder M P
# Title Pattern Diff Sources 208 Implement Trie Trie basic M N,B,G 211 Design Add and Search Words Trie + DFS wildcards M N,B 212 Word Search II Trie + Backtracking H N,B,G,H 648 Replace Words Trie M P 1268 Search Suggestions System Trie / Sort+BS M P
# Title Pattern Diff Sources 703 Kth Largest in Stream Min-heap of size k E N 1046 Last Stone Weight Max-heap E N,G 973 K Closest Points to Origin Min-heap by distance M N,G 215 Kth Largest Element in Array Heap / Quickselect M N,B,G 621 Task Scheduler Heap + cooldown M N,B 355 Design Twitter Heap + map M N 295 Find Median from Data Stream Two heaps H N,B,G,H 502 IPO Two heaps (min on cost, max on profit) H H 632 Smallest Range Covering K Lists Heap + sliding H H 1834 Single-Threaded CPU Heap by processing time M P
# Title Pattern Diff Sources 78 Subsets Backtracking M N,B,G 39 Combination Sum Backtracking + reuse M N,B,G 40 Combination Sum II Backtracking + dedupe M N 46 Permutations Backtracking M N,B,G 90 Subsets II Backtracking + dedupe M N 79 Word Search DFS + backtracking M N,B,G 131 Palindrome Partitioning Backtracking M N,B 17 Letter Combinations of a Phone Number Backtracking M N,G 51 N-Queens Backtracking H N,B,G,H 698 Partition to K Equal Sum Subsets Backtracking + bitmask M P
# Title Pattern Diff Sources 200 Number of Islands DFS / BFS / Union-Find M N,B,G 695 Max Area of Island DFS M G 133 Clone Graph DFS + map M N,B 207 Course Schedule Topo Sort M N,B,G 210 Course Schedule II Topo Sort M N,G 417 Pacific Atlantic Water Flow Multi-source DFS M N 130 Surrounded Regions DFS from boundary M N,B 994 Rotting Oranges Multi-source BFS M N,B 286 Walls and Gates Multi-source BFS M N 127 Word Ladder BFS on transformations H N,B,G,H 261 Graph Valid Tree Union-Find / DFS M N 323 Number of Connected Components Union-Find M N 547 Number of Provinces Union-Find / DFS M G,S 684 Redundant Connection Union-Find M P 743 Network Delay Time Dijkstra M N 787 Cheapest Flights Within K Stops Bellman-Ford / BFS M N 1584 Min Cost to Connect All Points Prim/Kruskal MST M N 778 Swim in Rising Water Dijkstra / Union-Find H N,H 332 Reconstruct Itinerary Hierholzer (Eulerian) H N,H 269 Alien Dictionary Topo Sort H N,B,G,H 305 Number of Islands II Union-Find dynamic H H 1976 Number of Ways to Arrive at Destination Dijkstra + DP M P
# Title Pattern Diff Sources 1192 Critical Connections Tarjan bridges H H 685 Redundant Connection II Union-Find directed H H 802 Find Eventual Safe States Reverse topo / DFS color M P 815 Bus Routes BFS on routes H H 1334 Find the City With Smallest Number of Reachable Neighbors Floyd-Warshall M P 847 Shortest Path Visiting All Nodes BFS + bitmask H H 1631 Path With Minimum Effort Dijkstra / BS+BFS M P 924 Minimize Malware Spread Union-Find + counting H H
# Title Pattern Diff Sources 70 Climbing Stairs DP basic E N,B,G 198 House Robber DP take-or-skip M N,B,G 213 House Robber II DP circular M N 5 Longest Palindromic Substring DP / expand M N,B,G 647 Palindromic Substrings DP / expand M N 91 Decode Ways DP M N,B 322 Coin Change Unbounded Knapsack DP M N,B,G 152 Maximum Product Subarray DP min/max M N,B 139 Word Break DP + Trie M N,B,G 300 Longest Increasing Subsequence DP / patience BS M N,B,G 416 Partition Equal Subset Sum 0/1 Knapsack M N 746 Min Cost Climbing Stairs DP basic E G 32 Longest Valid Parentheses DP / Stack H H,P 132 Palindrome Partitioning II DP min cuts H H
# Title Pattern Diff Sources 62 Unique Paths Grid DP M N,B,G 63 Unique Paths II Grid DP w/ obstacles M G 1143 Longest Common Subsequence DP table M N,B,G 309 Best Time to Buy/Sell Stock with Cooldown DP states M N,B 518 Coin Change 2 Unbounded knapsack count M N 494 Target Sum DP / Knapsack M N 97 Interleaving String DP table M N 329 Longest Increasing Path in a Matrix DP + DFS memo H N,H 115 Distinct Subsequences DP table H N,H 72 Edit Distance DP table H N,B,G,H 312 Burst Balloons Interval DP H N,H 10 Regular Expression Matching DP table H N,H 174 Dungeon Game DP back-prop H H 887 Super Egg Drop DP + BS H H
# Title Pattern Diff Sources 53 Maximum Subarray Kadane M N,B 55 Jump Game Greedy farthest M N,B,G 45 Jump Game II Greedy BFS-like M N 134 Gas Station Greedy M N 846 Hand of Straights Greedy + map M N 1899 Merge Triplets to Form Target Greedy filter M N 763 Partition Labels Greedy + last-occurrence M N,G 678 Valid Parenthesis String Greedy / two stacks M N 56 Merge Intervals Sort + merge M N,B,G 435 Non-overlapping Intervals Greedy by end M N,B
# Title Pattern Diff Sources 57 Insert Interval Merge M N,B,G 252 Meeting Rooms Sort by start E N 253 Meeting Rooms II Heap of end-times M N,B,G 1851 Min Interval to Include Each Query Heap + sort H N,H 986 Interval List Intersections Two Pointers M P 218 The Skyline Problem Heap + sweep H H
# Title Pattern Diff Sources 202 Happy Number Cycle detection E P 50 Pow(x, n) Fast exponentiation M N,B,G 66 Plus One Math sim E N 9 Palindrome Number Reverse half E G 7 Reverse Integer Math + overflow M G 8 String to Integer (atoi) Parsing M G 43 Multiply Strings String math M P 149 Max Points on a Line Hash slope H H 233 Number of Digit One Digit DP / math H H 372 Super Pow Modular exponentiation M P
# Title Pattern Diff Sources 136 Single Number XOR E N,B,G 137 Single Number II Bit count mod 3 M P 191 Number of 1 Bits Brian Kernighan E N 338 Counting Bits DP + bit E N,B 190 Reverse Bits Bit ops E N,B 268 Missing Number XOR / sum E N 371 Sum of Two Integers Bit add M N 7 Reverse Integer Overflow check M N
These are "design X" coding problems — they bridge DSA and LLD.
# Title Pattern Diff Sources 146 LRU Cache Hash + DLL M N,B,G 460 LFU Cache Two-level hash + DLL H H 380 Insert Delete GetRandom O(1) Hash + Array swap-remove M N,P 381 Insert Delete GetRandom O(1) Allow Duplicates Hash + Array H H 432 All O`one Data Structure DLL of buckets + hash H H 295 Find Median from Data Stream Two heaps H N 355 Design Twitter Heap + map M N 1166 Design File System Trie M P 1396 Design Underground System Hash maps M P 706 Design HashMap Bucket array E P 707 Design Linked List Linked list ops M P 622 Design Circular Queue Array + ptrs M P 641 Design Circular Deque Array + ptrs M P 588 Design In-Memory File System Trie + map H H 642 Design Search Autocomplete System Trie + heap H H
19 topics, 254 problems. Adjust ±5 during execution if duplicates collapse.
Note : a few problems appear in two topics (e.g. 53 in arrays-hashing and greedy, 121 in arrays-hashing and sliding-window, 7 in math and bit). The canonical file lives in the topic listed first; other appearances are aliases via Similar Problems cross-link only — no duplicate file.
Canonical assignment when duplicated:
53 -> arrays-hashing (Kadane is the headline)
121 -> arrays-hashing (one-pass min, not classical window)
152 -> dp-1d (DP track min/max is the headline)
7 -> math-geometry
295 -> heap-priority-queue (system-design-coding row references it)
146 -> linked-list (system-design-coding row references it)
355 -> heap-priority-queue (system-design-coding row references it)
Final canonical count: 226 unique problem files in topics/**/problems/*.md (one file per LeetCode number; deduped: 152 only under dp-1d/, 121 / 7 / 53 / 146 / 295 / 355 each appear once per canonical topic assignment).
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