Phase I — Linear Structures (Week 1)
1. Hash-Based Lookup — builds on nothing
| Set |
LC # |
Problem |
| 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
| Set |
LC # |
Problem |
| 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
| Set |
LC # |
Problem |
| 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
| Set |
LC # |
Problem |
| 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
| Set |
LC # |
Problem |
| 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
| Set |
LC # |
Problem |
| 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
| Set |
LC # |
Problem |
| 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 |
Phase II — Nodal & Grid Structures (Week 2)
8. Linked List — independent primitive
| Set |
LC # |
Problem |
| 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
| Set |
LC # |
Problem |
| 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
| Set |
LC # |
Problem |
| A |
48 |
Rotate Image |
| A |
54 |
Spiral Matrix |
| A |
73 |
Set Matrix Zeroes |
| B |
36 |
Valid Sudoku |
| B |
289 |
Game of Life |
Phase III — Hierarchical Structures (Week 3)
11. Tree DFS — builds on recursion
| Set |
LC # |
Problem |
| 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
| Set |
LC # |
Problem |
| 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
| Set |
LC # |
Problem |
| 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 — builds on trees (implicit tree over array)
| Set |
LC # |
Problem |
| 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
| Set |
LC # |
Problem |
| A |
208 |
Implement Trie |
| A |
211 |
Add & Search Words |
| B |
212 |
Word Search II (needs topic 20 — schedule after) |
Phase IV — Relational Structures (Week 4)
16. Graph DFS — builds on 11 + visited set
| Set |
LC # |
Problem |
| 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
| Set |
LC # |
Problem |
| 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
| Set |
LC # |
Problem |
| 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
| Set |
LC # |
Problem |
| A |
684 |
Redundant Connection |
| A |
323 |
Number of Connected Components |
| B |
128 |
Longest Consecutive (union-find variant) |
| B |
721 |
Accounts Merge |
Phase V — Decision-Space Exploration (Weeks 4–5)
20. Backtracking — builds on 16
| Set |
LC # |
Problem |
| 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 |
(Now unlock 212 Word Search II from topic 15.)
21. 1-D Dynamic Programming — builds on 20
| Set |
LC # |
Problem |
| 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
| Set |
LC # |
Problem |
| 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
| Set |
LC # |
Problem |
| A |
53 |
Maximum Subarray (Kadane's) |
| 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
| Set |
LC # |
Problem |
| 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 |
920 |
Meeting Rooms I |
