NeetCode 250 problem tracker¶

At a glance

Priority: P0 · Complexity: ⅕ · Est. time: ongoing (about 7-12 problems per week) · Phase: 1-6 · Prereqs: Approach & complexity, Python idioms You're done when: all 150 NeetCode 150 core problems are ticked and solved within the time-box, every failed problem has been re-solved on days 1, 3, 7 and 21, and you can solve a random unseen Medium in 25 minutes and a Hard in 40.

Why it matters¶

Volume with reflection builds pattern recognition, and a tracker keeps you honest. This master list has 265 problems grouped by pattern: the 150 NeetCode 150 core set (NC150) plus 115 extra problems (NC250+) chosen for Staff-level FAANG coverage (harder variants, classic follow-ups, and the concurrency/LLD set). Ordering inside each pattern is Easy, then Medium, then Hard. The "Week" column follows the roadmap phases in topics.yml.

How to use this page¶

Time-boxing (the 25-35 minute rule)¶

Minute	Action
0-5	Restate the problem, examples, constraints, target complexity
5-10	Brute force + complexity, then name the pattern
10-25	Implement and trace one example
25-35	Still stuck? Stop. Read or watch the solution, then close it
After	Re-implement from memory without looking, then write a 2-line "key insight" in your notes

Never grind past 35 minutes on a first attempt: after that you learn little and burn energy. Hards get 40-45 minutes.

Spaced-repetition rule (re-solve on day 1, 3, 7, 21)¶

Every problem that needed a hint, took over the time-box, or had a bug gets scheduled for re-solve from scratch, no notes:

Attempt	When	Pass criterion
R0	Day 0	First attempt (with the 35-minute box)
R1	Day 1	Solve unaided in the time-box
R2	Day 3	Solve unaided in ≤ 20 min
R3	Day 7	Solve unaided in ≤ 15 min, and explain the complexity out loud
R4	Day 21	Solve unaided in ≤ 15 min; retire the problem

A failed re-solve resets the ladder to R0. Keep a simple sheet (or a progress note) with columns: problem, first-solved date, next-due date, ladder step. Aim for 30-40% of each session on re-solves in revision weeks.

Weekly rhythm (12-15 h/week total, DSA about 3-4 h)¶

Slot	Activity
Weekdays (about 30-45 min)	1-2 new problems from this week's list, timed
Saturday	2-3 harder problems + mock-style: talk aloud, no IDE
Sunday	Re-solve queue (due R1-R4 items) + update the tracker
Checkpoint weeks 4/8/12/16/20	Mostly revision: re-solve failed problems, one 45-min mock
Week 24	Mock interviews only (no new problems)
Weeks 25-26 (buffer)	Catch-up on stretch problems

Schedule assumptions: no curriculum.yml was available when this page was generated, so weeks are computed from each pattern's phase (phase 1 starts week 1, phase 2 week 5, phase 3 week 9, phase 4 week 13, phase 5 week 17, phase 6 week 21). Core problems are scheduled first (max 8 per week, 3 on checkpoint weeks), and stretch problems fill remaining capacity once their pattern has started. If data/curriculum.yml moves a phase, shift the week numbers accordingly.

Week summary¶

Week	Core (NC150)	Stretch	Patterns	Note
W01	8	4	Arrays & hashing
W02	8	4	Arrays & hashing, Two pointers, Sliding window
W03	8	4	Arrays & hashing, Two pointers, Sliding window, Stack
W04	3	2	Two pointers, Stack	Checkpoint / revision week
W05	8	4	Two pointers, Sliding window, Binary search, Linked list
W06	8	4	Sliding window, Linked list
W07	8	4	Sliding window, Stack, Linked list, Trees
W08	3	2	Stack, Trees	Checkpoint / revision week
W09	8	4	Stack, Trees, Tries
W10	8	4	Binary search, Tries, Heap
W11	8	4	Binary search, Backtracking
W12	3	2	Linked list, Backtracking, Graphs	Checkpoint / revision week
W13	8	4	Linked list, Trees, Graphs
W14	8	4	Trees, Tries, Graphs, Advanced graphs
W15	8	4	Tries, Heap, Advanced graphs, DP 1-D
W16	3	2	Heap, DP 1-D	Checkpoint / revision week
W17	8	4	Heap, Backtracking, DP 1-D, DP 2-D
W18	8	4	Backtracking, DP 2-D, Greedy
W19	8	4	Backtracking, Graphs, Greedy, Intervals
W20	3	2	Graphs, Intervals	Checkpoint / revision week
W21	8	4	Math & bits, Concurrency & LLD
W22	7	5	Math & bits, Concurrency & LLD
W23	0	12	Graphs, Advanced graphs, Concurrency & LLD
W24	0	0	-	Checkpoint / revision week; Mock interviews only
W25	0	12	DP 1-D, DP 2-D, Greedy	Buffer
W26	0	12	Greedy, Intervals, Math & bits	Buffer

Master checklist¶

Status legend: [ ] not started, [~] in progress / needs re-solve, [x] done (R4 passed). Edit the status cell by hand as you go. The tracker is a plain table so it renders everywhere.

Arrays & hashing¶

Pattern page: Arrays & hashing · Phase 1

#	Problem	Difficulty	Pattern	Set	Week	Status
1	217. Contains Duplicate	Easy	Arrays & hashing	NC150	W01	[ ]
2	242. Valid Anagram	Easy	Arrays & hashing	NC150	W01	[ ]
3	1. Two Sum	Easy	Arrays & hashing	NC150	W01	[ ]
4	1929. Concatenation of Array	Easy	Arrays & hashing	NC250+	W01	[ ]
5	14. Longest Common Prefix	Easy	Arrays & hashing	NC250+	W01	[ ]
6	169. Majority Element	Easy	Arrays & hashing	NC250+	W01	[ ]
7	706. Design HashMap	Easy	Arrays & hashing	NC250+	W01	[ ]
8	49. Group Anagrams	Medium	Arrays & hashing	NC150	W01	[ ]
9	347. Top K Frequent Elements	Medium	Arrays & hashing	NC150	W01	[ ]
10	271. Encode and Decode Strings	Medium	Arrays & hashing	NC150	W01	[ ]
11	238. Product of Array Except Self	Medium	Arrays & hashing	NC150	W01	[ ]
12	36. Valid Sudoku	Medium	Arrays & hashing	NC150	W01	[ ]
13	128. Longest Consecutive Sequence	Medium	Arrays & hashing	NC150	W02	[ ]
14	560. Subarray Sum Equals K	Medium	Arrays & hashing	NC250+	W02	[ ]
15	75. Sort Colors	Medium	Arrays & hashing	NC250+	W02	[ ]
16	912. Sort an Array	Medium	Arrays & hashing	NC250+	W02	[ ]
17	229. Majority Element II	Medium	Arrays & hashing	NC250+	W02	[ ]
18	41. First Missing Positive	Hard	Arrays & hashing	NC250+	W03	[ ]

Two pointers¶

Pattern page: Two pointers · Phase 1

#	Problem	Difficulty	Pattern	Set	Week	Status
19	125. Valid Palindrome	Easy	Two pointers	NC150	W02	[ ]
20	344. Reverse String	Easy	Two pointers	NC250+	W03	[ ]
21	88. Merge Sorted Array	Easy	Two pointers	NC250+	W03	[ ]
22	283. Move Zeroes	Easy	Two pointers	NC250+	W03	[ ]
23	26. Remove Duplicates from Sorted Array	Easy	Two pointers	NC250+	W04	[ ]
24	680. Valid Palindrome II	Easy	Two pointers	NC250+	W04	[ ]
25	167. Two Sum II - Input Array Is Sorted	Medium	Two pointers	NC150	W02	[ ]
26	15. 3Sum	Medium	Two pointers	NC150	W02	[ ]
27	18. 4Sum	Medium	Two pointers	NC250+	W05	[ ]
28	11. Container With Most Water	Medium	Two pointers	NC150	W02	[ ]
29	881. Boats to Save People	Medium	Two pointers	NC250+	W05	[ ]
30	189. Rotate Array	Medium	Two pointers	NC250+	W05	[ ]
31	42. Trapping Rain Water	Hard	Two pointers	NC150	W02	[ ]

Sliding window¶

Pattern page: Sliding window · Phase 1

#	Problem	Difficulty	Pattern	Set	Week	Status
32	121. Best Time to Buy and Sell Stock	Easy	Sliding window	NC150	W02	[ ]
33	219. Contains Duplicate II	Easy	Sliding window	NC250+	W05	[ ]
34	3. Longest Substring Without Repeating Characters	Medium	Sliding window	NC150	W02	[ ]
35	424. Longest Repeating Character Replacement	Medium	Sliding window	NC150	W03	[ ]
36	567. Permutation in String	Medium	Sliding window	NC150	W03	[ ]
37	209. Minimum Size Subarray Sum	Medium	Sliding window	NC250+	W06	[ ]
38	1004. Max Consecutive Ones III	Medium	Sliding window	NC250+	W06	[ ]
39	438. Find All Anagrams in a String	Medium	Sliding window	NC250+	W06	[ ]
40	904. Fruit Into Baskets	Medium	Sliding window	NC250+	W06	[ ]
41	76. Minimum Window Substring	Hard	Sliding window	NC150	W03	[ ]
42	239. Sliding Window Maximum	Hard	Sliding window	NC150	W03	[ ]
43	992. Subarrays with K Different Integers	Hard	Sliding window	NC250+	W07	[ ]

Stack¶

Pattern page: Stack · Phase 1

#	Problem	Difficulty	Pattern	Set	Week	Status
44	20. Valid Parentheses	Easy	Stack	NC150	W03	[ ]
45	682. Baseball Game	Easy	Stack	NC250+	W07	[ ]
46	225. Implement Stack using Queues	Easy	Stack	NC250+	W07	[ ]
47	155. Min Stack	Medium	Stack	NC150	W03	[ ]
48	150. Evaluate Reverse Polish Notation	Medium	Stack	NC150	W03	[ ]
49	22. Generate Parentheses	Medium	Stack	NC150	W03	[ ]
50	739. Daily Temperatures	Medium	Stack	NC150	W04	[ ]
51	853. Car Fleet	Medium	Stack	NC150	W04	[ ]
52	71. Simplify Path	Medium	Stack	NC250+	W07	[ ]
53	394. Decode String	Medium	Stack	NC250+	W08	[ ]
54	735. Asteroid Collision	Medium	Stack	NC250+	W08	[ ]
55	901. Online Stock Span	Medium	Stack	NC250+	W09	[ ]
56	402. Remove K Digits	Medium	Stack	NC250+	W09	[ ]
57	907. Sum of Subarray Minimums	Medium	Stack	NC250+	W09	[ ]
58	84. Largest Rectangle in Histogram	Hard	Stack	NC150	W04	[ ]
59	85. Maximal Rectangle	Hard	Stack	NC250+	W09	[ ]

Binary search¶

Pattern page: Binary search · Phase 2

#	Problem	Difficulty	Pattern	Set	Week	Status
60	704. Binary Search	Easy	Binary search	NC150	W05	[ ]
61	35. Search Insert Position	Easy	Binary search	NC250+	W10	[ ]
62	374. Guess Number Higher or Lower	Easy	Binary search	NC250+	W10	[ ]
63	69. Sqrt(x)	Easy	Binary search	NC250+	W10	[ ]
64	74. Search a 2D Matrix	Medium	Binary search	NC150	W05	[ ]
65	875. Koko Eating Bananas	Medium	Binary search	NC150	W05	[ ]
66	153. Find Minimum in Rotated Sorted Array	Medium	Binary search	NC150	W05	[ ]
67	33. Search in Rotated Sorted Array	Medium	Binary search	NC150	W05	[ ]
68	981. Time Based Key-Value Store	Medium	Binary search	NC150	W05	[ ]
69	34. Find First and Last Position of Element in Sorted Array	Medium	Binary search	NC250+	W10	[ ]
70	162. Find Peak Element	Medium	Binary search	NC250+	W11	[ ]
71	1011. Capacity To Ship Packages Within D Days	Medium	Binary search	NC250+	W11	[ ]
72	81. Search in Rotated Sorted Array II	Medium	Binary search	NC250+	W11	[ ]
73	410. Split Array Largest Sum	Hard	Binary search	NC250+	W11	[ ]
74	4. Median of Two Sorted Arrays	Hard	Binary search	NC150	W05	[ ]

Linked list¶

Pattern page: Linked list · Phase 2

#	Problem	Difficulty	Pattern	Set	Week	Status
75	206. Reverse Linked List	Easy	Linked list	NC150	W05	[ ]
76	21. Merge Two Sorted Lists	Easy	Linked list	NC150	W06	[ ]
77	141. Linked List Cycle	Easy	Linked list	NC150	W06	[ ]
78	234. Palindrome Linked List	Easy	Linked list	NC250+	W12	[ ]
79	143. Reorder List	Medium	Linked list	NC150	W06	[ ]
80	19. Remove Nth Node From End of List	Medium	Linked list	NC150	W06	[ ]
81	138. Copy List with Random Pointer	Medium	Linked list	NC150	W06	[ ]
82	2. Add Two Numbers	Medium	Linked list	NC150	W06	[ ]
83	287. Find the Duplicate Number	Medium	Linked list	NC150	W06	[ ]
84	142. Linked List Cycle II	Medium	Linked list	NC250+	W12	[ ]
85	92. Reverse Linked List II	Medium	Linked list	NC250+	W13	[ ]
86	146. LRU Cache	Medium	Linked list	NC150	W06	[ ]
87	23. Merge k Sorted Lists	Hard	Linked list	NC150	W07	[ ]
88	25. Reverse Nodes in k-Group	Hard	Linked list	NC150	W07	[ ]

Trees¶

Pattern page: Trees · Phase 2

#	Problem	Difficulty	Pattern	Set	Week	Status
89	94. Binary Tree Inorder Traversal	Easy	Trees	NC250+	W13	[ ]
90	226. Invert Binary Tree	Easy	Trees	NC150	W07	[ ]
91	104. Maximum Depth of Binary Tree	Easy	Trees	NC150	W07	[ ]
92	543. Diameter of Binary Tree	Easy	Trees	NC150	W07	[ ]
93	110. Balanced Binary Tree	Easy	Trees	NC150	W07	[ ]
94	100. Same Tree	Easy	Trees	NC150	W07	[ ]
95	572. Subtree of Another Tree	Easy	Trees	NC150	W07	[ ]
96	235. Lowest Common Ancestor of a Binary Search Tree	Medium	Trees	NC150	W08	[ ]
97	102. Binary Tree Level Order Traversal	Medium	Trees	NC150	W08	[ ]
98	199. Binary Tree Right Side View	Medium	Trees	NC150	W08	[ ]
99	103. Binary Tree Zigzag Level Order Traversal	Medium	Trees	NC250+	W13	[ ]
100	1448. Count Good Nodes in Binary Tree	Medium	Trees	NC150	W09	[ ]
101	98. Validate Binary Search Tree	Medium	Trees	NC150	W09	[ ]
102	230. Kth Smallest Element in a BST	Medium	Trees	NC150	W09	[ ]
103	105. Construct Binary Tree from Preorder and Inorder Traversal	Medium	Trees	NC150	W09	[ ]
104	236. Lowest Common Ancestor of a Binary Tree	Medium	Trees	NC250+	W13	[ ]
105	450. Delete Node in a BST	Medium	Trees	NC250+	W14	[ ]
106	124. Binary Tree Maximum Path Sum	Hard	Trees	NC150	W09	[ ]
107	297. Serialize and Deserialize Binary Tree	Hard	Trees	NC150	W09	[ ]

Tries¶

Pattern page: Tries · Phase 3

#	Problem	Difficulty	Pattern	Set	Week	Status
108	208. Implement Trie (Prefix Tree)	Medium	Tries	NC150	W09	[ ]
109	211. Design Add and Search Words Data Structure	Medium	Tries	NC150	W09	[ ]
110	720. Longest Word in Dictionary	Medium	Tries	NC250+	W14	[ ]
111	648. Replace Words	Medium	Tries	NC250+	W14	[ ]
112	1268. Search Suggestions System	Medium	Tries	NC250+	W14	[ ]
113	421. Maximum XOR of Two Numbers in an Array	Medium	Tries	NC250+	W15	[ ]
114	212. Word Search II	Hard	Tries	NC150	W10	[ ]
115	336. Palindrome Pairs	Hard	Tries	NC250+	W15	[ ]

Heap¶

Pattern page: Heap · Phase 3

#	Problem	Difficulty	Pattern	Set	Week	Status
116	703. Kth Largest Element in a Stream	Easy	Heap	NC150	W10	[ ]
117	1046. Last Stone Weight	Easy	Heap	NC150	W10	[ ]
118	973. K Closest Points to Origin	Medium	Heap	NC150	W10	[ ]
119	215. Kth Largest Element in an Array	Medium	Heap	NC150	W10	[ ]
120	621. Task Scheduler	Medium	Heap	NC150	W10	[ ]
121	355. Design Twitter	Medium	Heap	NC150	W10	[ ]
122	767. Reorganize String	Medium	Heap	NC250+	W15	[ ]
123	1405. Longest Happy String	Medium	Heap	NC250+	W15	[ ]
124	1834. Single-Threaded CPU	Medium	Heap	NC250+	W16	[ ]
125	373. Find K Pairs with Smallest Sums	Medium	Heap	NC250+	W16	[ ]
126	295. Find Median from Data Stream	Hard	Heap	NC150	W10	[ ]
127	502. IPO	Hard	Heap	NC250+	W17	[ ]
128	480. Sliding Window Median	Hard	Heap	NC250+	W17	[ ]

Backtracking¶

Pattern page: Backtracking · Phase 3

#	Problem	Difficulty	Pattern	Set	Week	Status
129	1863. Sum of All Subset XOR Totals	Easy	Backtracking	NC250+	W17	[ ]
130	78. Subsets	Medium	Backtracking	NC150	W11	[ ]
131	39. Combination Sum	Medium	Backtracking	NC150	W11	[ ]
132	40. Combination Sum II	Medium	Backtracking	NC150	W11	[ ]
133	77. Combinations	Medium	Backtracking	NC250+	W17	[ ]
134	46. Permutations	Medium	Backtracking	NC150	W11	[ ]
135	90. Subsets II	Medium	Backtracking	NC150	W11	[ ]
136	47. Permutations II	Medium	Backtracking	NC250+	W18	[ ]
137	79. Word Search	Medium	Backtracking	NC150	W11	[ ]
138	131. Palindrome Partitioning	Medium	Backtracking	NC150	W11	[ ]
139	17. Letter Combinations of a Phone Number	Medium	Backtracking	NC150	W11	[ ]
140	473. Matchsticks to Square	Medium	Backtracking	NC250+	W18	[ ]
141	698. Partition to K Equal Sum Subsets	Medium	Backtracking	NC250+	W18	[ ]
142	51. N-Queens	Hard	Backtracking	NC150	W12	[ ]
143	52. N-Queens II	Hard	Backtracking	NC250+	W18	[ ]
144	37. Sudoku Solver	Hard	Backtracking	NC250+	W19	[ ]

Graphs¶

Pattern page: Graphs · Phase 3

#	Problem	Difficulty	Pattern	Set	Week	Status
145	733. Flood Fill	Easy	Graphs	NC250+	W19	[ ]
146	463. Island Perimeter	Easy	Graphs	NC250+	W19	[ ]
147	200. Number of Islands	Medium	Graphs	NC150	W12	[ ]
148	695. Max Area of Island	Medium	Graphs	NC150	W12	[ ]
149	133. Clone Graph	Medium	Graphs	NC150	W13	[ ]
150	286. Walls and Gates	Medium	Graphs	NC150	W13	[ ]
151	994. Rotting Oranges	Medium	Graphs	NC150	W13	[ ]
152	417. Pacific Atlantic Water Flow	Medium	Graphs	NC150	W13	[ ]
153	130. Surrounded Regions	Medium	Graphs	NC150	W13	[ ]
154	207. Course Schedule	Medium	Graphs	NC150	W13	[ ]
155	210. Course Schedule II	Medium	Graphs	NC150	W13	[ ]
156	684. Redundant Connection	Medium	Graphs	NC150	W13	[ ]
157	323. Number of Connected Components in an Undirected Graph	Medium	Graphs	NC150	W14	[ ]
158	261. Graph Valid Tree	Medium	Graphs	NC150	W14	[ ]
159	1091. Shortest Path in Binary Matrix	Medium	Graphs	NC250+	W19	[ ]
160	1466. Reorder Routes to Make All Paths Lead to the City Zero	Medium	Graphs	NC250+	W20	[ ]
161	399. Evaluate Division	Medium	Graphs	NC250+	W20	[ ]
162	721. Accounts Merge	Medium	Graphs	NC250+	W23	[ ]
163	909. Snakes and Ladders	Medium	Graphs	NC250+	W23	[ ]
164	752. Open the Lock	Medium	Graphs	NC250+	W23	[ ]
165	127. Word Ladder	Hard	Graphs	NC150	W14	[ ]

Advanced graphs¶

Pattern page: Advanced graphs · Phase 4

#	Problem	Difficulty	Pattern	Set	Week	Status
166	743. Network Delay Time	Medium	Advanced graphs	NC150	W14	[ ]
167	1584. Min Cost to Connect All Points	Medium	Advanced graphs	NC150	W14	[ ]
168	787. Cheapest Flights Within K Stops	Medium	Advanced graphs	NC150	W14	[ ]
169	1514. Path with Maximum Probability	Medium	Advanced graphs	NC250+	W23	[ ]
170	1631. Path With Minimum Effort	Medium	Advanced graphs	NC250+	W23	[ ]
171	332. Reconstruct Itinerary	Hard	Advanced graphs	NC150	W14	[ ]
172	778. Swim in Rising Water	Hard	Advanced graphs	NC150	W14	[ ]
173	269. Alien Dictionary	Hard	Advanced graphs	NC150	W15	[ ]
174	2392. Build a Matrix With Conditions	Hard	Advanced graphs	NC250+	W23	[ ]
175	1192. Critical Connections in a Network	Hard	Advanced graphs	NC250+	W23	[ ]
176	1489. Find Critical and Pseudo-Critical Edges in Minimum Spanning Tree	Hard	Advanced graphs	NC250+	W23	[ ]

DP 1-D¶

Pattern page: DP 1-D · Phase 4

#	Problem	Difficulty	Pattern	Set	Week	Status
177	70. Climbing Stairs	Easy	DP 1-D	NC150	W15	[ ]
178	746. Min Cost Climbing Stairs	Easy	DP 1-D	NC150	W15	[ ]
179	1137. N-th Tribonacci Number	Easy	DP 1-D	NC250+	W25	[ ]
180	198. House Robber	Medium	DP 1-D	NC150	W15	[ ]
181	213. House Robber II	Medium	DP 1-D	NC150	W15	[ ]
182	5. Longest Palindromic Substring	Medium	DP 1-D	NC150	W15	[ ]
183	647. Palindromic Substrings	Medium	DP 1-D	NC150	W15	[ ]
184	91. Decode Ways	Medium	DP 1-D	NC150	W15	[ ]
185	322. Coin Change	Medium	DP 1-D	NC150	W16	[ ]
186	152. Maximum Product Subarray	Medium	DP 1-D	NC150	W16	[ ]
187	139. Word Break	Medium	DP 1-D	NC150	W16	[ ]
188	300. Longest Increasing Subsequence	Medium	DP 1-D	NC150	W17	[ ]
189	416. Partition Equal Subset Sum	Medium	DP 1-D	NC150	W17	[ ]
190	279. Perfect Squares	Medium	DP 1-D	NC250+	W25	[ ]
191	377. Combination Sum IV	Medium	DP 1-D	NC250+	W25	[ ]
192	740. Delete and Earn	Medium	DP 1-D	NC250+	W25	[ ]
193	368. Largest Divisible Subset	Medium	DP 1-D	NC250+	W25	[ ]
194	354. Russian Doll Envelopes	Hard	DP 1-D	NC250+	W25	[ ]

DP 2-D¶

Pattern page: DP 2-D · Phase 5

#	Problem	Difficulty	Pattern	Set	Week	Status
195	62. Unique Paths	Medium	DP 2-D	NC150	W17	[ ]
196	63. Unique Paths II	Medium	DP 2-D	NC250+	W25	[ ]
197	64. Minimum Path Sum	Medium	DP 2-D	NC250+	W25	[ ]
198	1143. Longest Common Subsequence	Medium	DP 2-D	NC150	W17	[ ]
199	309. Best Time to Buy and Sell Stock with Cooldown	Medium	DP 2-D	NC150	W17	[ ]
200	518. Coin Change II	Medium	DP 2-D	NC150	W17	[ ]
201	494. Target Sum	Medium	DP 2-D	NC150	W17	[ ]
202	97. Interleaving String	Medium	DP 2-D	NC150	W17	[ ]
203	72. Edit Distance	Medium	DP 2-D	NC150	W18	[ ]
204	221. Maximal Square	Medium	DP 2-D	NC250+	W25	[ ]
205	474. Ones and Zeroes	Medium	DP 2-D	NC250+	W25	[ ]
206	329. Longest Increasing Path in a Matrix	Hard	DP 2-D	NC150	W18	[ ]
207	115. Distinct Subsequences	Hard	DP 2-D	NC150	W18	[ ]
208	188. Best Time to Buy and Sell Stock IV	Hard	DP 2-D	NC250+	W25	[ ]
209	312. Burst Balloons	Hard	DP 2-D	NC150	W18	[ ]
210	10. Regular Expression Matching	Hard	DP 2-D	NC150	W18	[ ]

Greedy¶

Pattern page: Greedy · Phase 5

#	Problem	Difficulty	Pattern	Set	Week	Status
211	860. Lemonade Change	Easy	Greedy	NC250+	W25	[ ]
212	53. Maximum Subarray	Medium	Greedy	NC150	W18	[ ]
213	122. Best Time to Buy and Sell Stock II	Medium	Greedy	NC250+	W26	[ ]
214	918. Maximum Sum Circular Subarray	Medium	Greedy	NC250+	W26	[ ]
215	978. Longest Turbulent Subarray	Medium	Greedy	NC250+	W26	[ ]
216	55. Jump Game	Medium	Greedy	NC150	W18	[ ]
217	45. Jump Game II	Medium	Greedy	NC150	W18	[ ]
218	134. Gas Station	Medium	Greedy	NC150	W19	[ ]
219	846. Hand of Straights	Medium	Greedy	NC150	W19	[ ]
220	1899. Merge Triplets to Form Target Triplet	Medium	Greedy	NC150	W19	[ ]
221	763. Partition Labels	Medium	Greedy	NC150	W19	[ ]
222	678. Valid Parenthesis String	Medium	Greedy	NC150	W19	[ ]
223	1029. Two City Scheduling	Medium	Greedy	NC250+	W26	[ ]
224	135. Candy	Hard	Greedy	NC250+	W26	[ ]

Intervals¶

Pattern page: Intervals · Phase 5

#	Problem	Difficulty	Pattern	Set	Week	Status
225	252. Meeting Rooms	Easy	Intervals	NC150	W19	[ ]
226	56. Merge Intervals	Medium	Intervals	NC150	W19	[ ]
227	57. Insert Interval	Medium	Intervals	NC150	W19	[ ]
228	435. Non-overlapping Intervals	Medium	Intervals	NC150	W20	[ ]
229	452. Minimum Number of Arrows to Burst Balloons	Medium	Intervals	NC250+	W26	[ ]
230	253. Meeting Rooms II	Medium	Intervals	NC150	W20	[ ]
231	986. Interval List Intersections	Medium	Intervals	NC250+	W26	[ ]
232	1288. Remove Covered Intervals	Medium	Intervals	NC250+	W26	[ ]
233	729. My Calendar I	Medium	Intervals	NC250+	W26	[ ]
234	1851. Minimum Interval to Include Each Query	Hard	Intervals	NC150	W20	[ ]
235	759. Employee Free Time	Hard	Intervals	NC250+	W26	[ ]

Math & bits¶

Pattern page: Math & bits · Phase 5

#	Problem	Difficulty	Pattern	Set	Week	Status
236	136. Single Number	Easy	Math & bits	NC150	W21	[ ]
237	191. Number of 1 Bits	Easy	Math & bits	NC150	W21	[ ]
238	338. Counting Bits	Easy	Math & bits	NC150	W21	[ ]
239	190. Reverse Bits	Easy	Math & bits	NC150	W21	[ ]
240	268. Missing Number	Easy	Math & bits	NC150	W21	[ ]
241	202. Happy Number	Easy	Math & bits	NC150	W21	[ ]
242	66. Plus One	Easy	Math & bits	NC150	W21	[ ]
243	371. Sum of Two Integers	Medium	Math & bits	NC150	W21	[ ]
244	7. Reverse Integer	Medium	Math & bits	NC150	W22	[ ]
245	48. Rotate Image	Medium	Math & bits	NC150	W22	[ ]
246	54. Spiral Matrix	Medium	Math & bits	NC150	W22	[ ]
247	73. Set Matrix Zeroes	Medium	Math & bits	NC150	W22	[ ]
248	50. Pow(x, n)	Medium	Math & bits	NC150	W22	[ ]
249	43. Multiply Strings	Medium	Math & bits	NC150	W22	[ ]
250	2013. Detect Squares	Medium	Math & bits	NC150	W22	[ ]
251	201. Bitwise AND of Numbers Range	Medium	Math & bits	NC250+	W26	[ ]
252	149. Max Points on a Line	Hard	Math & bits	NC250+	W26	[ ]

Concurrency & LLD¶

Pattern page: Concurrency & LLD · Phase 6

#	Problem	Difficulty	Pattern	Set	Week	Status
253	1114. Print in Order	Easy	Concurrency & LLD	NC250+	W21	[ ]
254	359. Logger Rate Limiter	Easy	Concurrency & LLD	NC250+	W21	[ ]
255	1115. Print FooBar Alternately	Medium	Concurrency & LLD	NC250+	W21	[ ]
256	1116. Print Zero Even Odd	Medium	Concurrency & LLD	NC250+	W21	[ ]
257	1117. Building H2O	Medium	Concurrency & LLD	NC250+	W22	[ ]
258	1195. Fizz Buzz Multithreaded	Medium	Concurrency & LLD	NC250+	W22	[ ]
259	1226. The Dining Philosophers	Medium	Concurrency & LLD	NC250+	W22	[ ]
260	1188. Design Bounded Blocking Queue	Medium	Concurrency & LLD	NC250+	W22	[ ]
261	1242. Web Crawler Multithreaded	Medium	Concurrency & LLD	NC250+	W22	[ ]
262	362. Design Hit Counter	Medium	Concurrency & LLD	NC250+	W23	[ ]
263	380. Insert Delete GetRandom O(1)	Medium	Concurrency & LLD	NC250+	W23	[ ]
264	1472. Design Browser History	Medium	Concurrency & LLD	NC250+	W23	[ ]
265	460. LFU Cache	Hard	Concurrency & LLD	NC250+	W23	[ ]

Notes¶

Premium LeetCode problems are marked "(Premium)" in each pattern page's insight column. NeetCode.io offers free access to the same problem statements (see the resources). If you do not have access, skip them: none is required for the core set except 271, 286, 323, 261 and 269 (substitute the NeetCode versions).
LeetCode returns 403 to scripted link checks (bot protection), so the problem URLs here were built from the official title slugs, not machine-verified. If a link 404s, search the number on leetcode.com.
Problem 146 (LRU Cache) appears once, under Linked list, and is repeated in the concurrency & LLD lab as an extension exercise.

Questions¶

L1 — Recall¶

Q1. State the spaced-repetition ladder and the pass criterion for retiring a problem.

Answer

Re-solve on day 1, 3, 7, 21 without notes. Retire it after the day-21 solve is done in ≤ 15 minutes with the complexity explained. A failure resets to day 0.

Q2. What is the time-box, and what do you do at its end?

Answer

25-35 minutes (40-45 for Hards). At the end, stop, read or watch one solution, close it, re-implement from memory, then write the key insight. Schedule R1.

Q3. What is the NC150 vs NC250+ distinction in this tracker?

Answer

NC150 is the NeetCode core interview set and is mandatory. NC250+ adds harder variants, Staff-level classics and concurrency/LLD problems, and is done as time allows (buffer weeks absorb overflow).

L2 — Apply¶

Q4. You are 3 days behind at the end of week 6. Re-plan.

Answer

Never drop NC150. Move that week's NC250+ problems into the next buffer or revision week, keep the re-solve queue (it is the highest-value activity), and cut the week's new problems to the ones in patterns due for the next checkpoint. If two weeks behind, push the P1 patterns (tries, advanced graphs, math and bits) into the buffer weeks 25-26.

Q5. Design your personal spreadsheet columns for the spaced-repetition queue.

Answer

Problem id, pattern, first-solved date, ladder step (R0-R4), next-due date (= first-solved + ⅓/7/21 days according to the step), last time (minutes), needed hint (y/n), failure reason (pattern-miss, bug, edge case, complexity). A filter on next-due ≤ today gives the daily queue.

Q6. After a mock you notice most failures are 'edge case bugs', not pattern misses. What do you change?

Answer

Add a mandatory 3-minute test phase to your loop (empty, single, duplicates, max size, negative), keep a personal bug log by category, practise tracing your code line by line instead of re-reading it, and add "edge cases" to the pass criterion of each re-solve.

L3 — Design & trade-offs¶

Q7. Breadth-first (all patterns once) vs depth-first (one pattern to mastery) for 24 weeks?

Answer

Use pattern-by-pattern progression for learning (this plan's phases), and interleave old patterns through the re-solve queue and checkpoint-week mixed sets, because interleaving improves discrimination ("which pattern is this?") and retention. Pure blocking makes every problem look like the current pattern's problem, which does not match real interviews.

Q8. How many problems are enough? Defend a number.

Answer

Around 150-250 well-reviewed problems is a common threshold for pattern fluency, but the number matters less than the quality of review. 150 with proper re-solving beats 500 solved once. Track the leading indicators instead: percent of unseen Mediums solved in 25 minutes without hints, and the failure-cause distribution from mocks.

Q9. How do you use company-tagged problem lists responsibly?

Answer

Use them for the last 2-3 weeks to calibrate difficulty and style, not as a shortcut. Prioritise pattern coverage first. Treat frequency data as weak evidence, since interviewers rotate questions and the tags are self-reported.

L4 — Staff-level ambiguity¶

Q10. You have a Staff loop in 4 weeks and are only at week 12 of this plan. What do you cut and keep?

Answer

Keep: all NC150 in trees, graphs, heap, DP 1-D, intervals and binary search (highest frequency), daily re-solves, and 2-3 mocks per week. Compress: DP 2-D and advanced graphs to the 6-8 most common problems (LCS, edit distance, coin change II, Dijkstra, topological sort, union-find). Drop: math/bit trivia, tries beyond the basic implementation, NC250+ entirely. Add: LLD/concurrency and one system-design mock per week, since Staff loops weigh these heavily. Communicate that trade-off to your recruiter if you need more time, because moving the date is often possible.

Q11. A colleague preparing with you memorises solutions. How do you help them shift?

Answer

Introduce the "explain to a rubber duck without code" exercise, ask them to derive the brute force and identify the inefficiency before reading hints, run mocks with a twist (change a constraint, for example negative numbers or streaming) so memorised solutions fail visibly, and give the re-solve ladder with a strict no-notes rule. The goal is derivation ability, so make that the measured outcome.

Real-world use cases¶

Personal learning ops: the same tracker-plus-spaced-repetition mechanic works for on-call runbook drills and incident-response practice.
Team interview prep groups: shared tracker for a peer study cohort (mock rotation).
Interviewer calibration: if you interview others, the tracker's difficulty ladder helps pick fair problems.

Pitfalls & anti-patterns¶

Solving a problem once and marking it done.
Watching solutions first ("passive learning").
Grinding past the time-box.
Only practising your strongest patterns.
No mock interviews (talking aloud is a separate skill).

Checklist¶

I created my spaced-repetition sheet with due dates
I use the 25-35 minute time-box on every first attempt
I completed at least one mock interview every checkpoint week
I answered all L3 questions out loud in < 3 min each