Phase I — Linear Structures (Week 1)

Topic	Set	LC #	Problem
1. Hash-Based Lookup builds on nothing	A	217	Contains Duplicate
	A	242	Valid Anagram
	A	1	Two Sum
	A	49	Group Anagrams
	A	347	Top K Frequent Elements
	B	383	Ransom Note
	B	205	Isomorphic Strings
	B	128	Longest Consecutive Sequence
	B	290	Word Pattern
2. Prefix Sum builds on 1	A	303	Range Sum Query
	A	238	Product of Array Except Self
	A	560	Subarray Sum Equals K
	B	525	Contiguous Array
	B	974	Subarray Sums Divisible by K
3. Two Pointers builds on ordered iteration	A	125	Valid Palindrome
	A	167	Two Sum II
	A	15	3Sum
	A	11	Container With Most Water
	A	42	Trapping Rain Water
	B	392	Is Subsequence
	B	977	Squares of a Sorted Array
	B	189	Rotate Array
	B	80	Remove Duplicates II
4. Sliding Window builds on 3	A	121	Best Time to Buy and Sell Stock
	A	3	Longest Substring Without Repeating Characters
	A	424	Longest Repeating Character Replacement
	A	567	Permutation in String
	A	76	Minimum Window Substring
	B	209	Minimum Size Subarray Sum
	B	1004	Max Consecutive Ones III
	B	643	Maximum Average Subarray
5. Binary Search builds on ordered / monotonic invariants	A	704	Binary Search
	A	74	Search a 2D Matrix
	A	875	Koko Eating Bananas
	A	33	Search in Rotated Sorted Array
	A	153	Find Minimum in Rotated Sorted Array
	B	35	Search Insert Position
	B	162	Find Peak Element
	B	34	First & Last Position
	B ⭐	4	Median of Two Sorted Arrays
6. Stack independent primitive	A	20	Valid Parentheses
	A	155	Min Stack
	A	150	Evaluate Reverse Polish Notation
	B	71	Simplify Path
	B ⭐	224	Basic Calculator
7. Monotonic Stack builds on 6	A	739	Daily Temperatures
	A	853	Car Fleet
	B	496	Next Greater Element I
	B	901	Online Stock Span
	B ⭐	84	Largest Rectangle in Histogram

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Phase II — Nodal & Grid Structures (Week 2)

Topic	Set	LC #	Problem
8. Linked List independent primitive	A	206	Reverse Linked List
	A	21	Merge Two Sorted Lists
	A	141	Linked List Cycle
	A	19	Remove Nth Node From End
	A	143	Reorder List
	B	876	Middle of the Linked List
	B	92	Reverse Linked List II
	B	82	Remove Duplicates from Sorted List II
	B	61	Rotate List
	B	86	Partition List
9. Hybrid Structures builds on 1 + 8	A	146	LRU Cache
	A	2	Add Two Numbers
	B	138	Copy List with Random Pointer
	B	380	Insert Delete GetRandom O(1)
10. Matrix Index Math builds on 3 — NOT graph traversal	A	48	Rotate Image
	A	54	Spiral Matrix
	A	73	Set Matrix Zeroes
	B	36	Valid Sudoku
	B	289	Game of Life

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Phase III — Hierarchical Structures (Week 3)

Topic	Set	LC #	Problem
11. Tree DFS builds on recursion	A	226	Invert Binary Tree
	A	104	Maximum Depth of Binary Tree
	A	100	Same Tree
	A	572	Subtree of Another Tree
	A	236	Lowest Common Ancestor
	A ⭐	124	Binary Tree Maximum Path Sum
	B	101	Symmetric Tree
	B	112	Path Sum
	B	129	Sum Root to Leaf Numbers
	B	543	Diameter of Binary Tree
12. Tree BFS builds on 6's sibling (queue) + 11	A	102	Level Order Traversal
	A	199	Right Side View
	A	1448	Count Good Nodes
	B	103	Zigzag Level Order
	B	637	Average of Levels
13. Binary Search Tree builds on 5 + 11	A	98	Validate BST
	A	230	Kth Smallest in BST
	A	235	LCA of BST
	A	105	Build from Preorder + Inorder
	B	530	Minimum Absolute Difference
	B	173	BST Iterator
	B	108	Sorted Array to BST
14. Heap / Priority Queue implicit tree over array	A	215	Kth Largest in Array
	A	703	Kth Largest in Stream
	A	973	K Closest Points
	A	621	Task Scheduler
	A	23	Merge K Sorted Lists
	B	1046	Last Stone Weight
	B	373	K Pairs with Smallest Sums
	B ⭐	295	Find Median from Data Stream
	B ⭐	502	IPO
15. Trie builds on 11	A	208	Implement Trie
	A	211	Add & Search Words
	B	212	Word Search II (needs topic 20 — schedule after)

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Phase IV — Relational Structures (Week 4)

Topic	Set	LC #	Problem
16. Graph DFS builds on 11 + visited set	A	200	Number of Islands
	A	695	Max Area of Island
	A	133	Clone Graph
	A	417	Pacific Atlantic Water Flow
	A	130	Surrounded Regions
	B	399	Evaluate Division
	B	261	Graph Valid Tree
17. Graph BFS builds on 12 + visited set — shortest path unweighted	A	994	Rotting Oranges
	A	127	Word Ladder
	B	909	Snakes and Ladders
	B	433	Minimum Genetic Mutation
	B	286	Walls and Gates
18. Topological Sort builds on 16	A	207	Course Schedule
	A	210	Course Schedule II
	B ⭐	269	Alien Dictionary
	B	1462	Course Schedule IV
19. Union-Find builds on 16's problem class	A	684	Redundant Connection
	A	323	Number of Connected Components
	B	128	Longest Consecutive (union-find variant)
	B	721	Accounts Merge

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Phase V — Decision-Space Exploration (Weeks 4–5)

Topic	Set	LC #	Problem
20. Backtracking builds on 16 — then unlock LC 212 from topic 15	A	78	Subsets
	A	39	Combination Sum
	A	46	Permutations
	A	79	Word Search
	B	17	Letter Combinations
	B	77	Combinations
	B	22	Generate Parentheses
	B ⭐	52	N-Queens II
21. 1-D Dynamic Programming builds on 20	A	70	Climbing Stairs
	A	746	Min Cost Climbing Stairs
	A	198	House Robber
	A	213	House Robber II
	A	322	Coin Change
	A	300	Longest Increasing Subsequence
	B	139	Word Break
	B	91	Decode Ways
	B	647	Palindromic Substrings
22. Multi-D / Grid DP builds on 21	A	62	Unique Paths
	A	64	Minimum Path Sum
	A	1143	Longest Common Subsequence
	B	120	Triangle
	B	63	Unique Paths II
	B ⭐	72	Edit Distance
	B	221	Maximal Square
	B ⭐	97	Interleaving String
23. Greedy builds on 21 — includes Kadane's	A	53	Maximum Subarray
	A	55	Jump Game
	A	45	Jump Game II
	A	134	Gas Station
	B	122	Best Time to Buy and Sell Stock II
	B	918	Maximum Sum Circular Subarray
	B	763	Partition Labels
24. Intervals builds on 23	A	57	Insert Interval
	A	56	Merge Intervals
	A	435	Non-Overlapping Intervals
	A	253	Meeting Rooms II
	B	228	Summary Ranges
	B	452	Minimum Arrows to Burst Balloons
	B	252	Meeting Rooms I