📚 Complete DSA Learning Roadmap

A structured, phase-by-phase roadmap for mastering Data Structures & Algorithms, paired with a curated list of 350 LeetCode problems organized by topic.

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🗺️ Roadmap Overview

Phase	Priority	Topic	Difficulty	Prerequisites	Why Learn?
1	⭐⭐⭐⭐⭐	1. Array	★☆☆☆☆	None	Most basic & common
1	⭐⭐⭐⭐⭐	2. String	★☆☆☆☆	Array	Same as arrays, huge in interviews
1	⭐⭐⭐⭐⭐	3. Hash Table	★★☆☆☆	Array	O(1) lookups, solves 50% of problems
1	⭐⭐⭐⭐☆	4. Linked List	★★☆☆☆	Array, Recursion	Pointer concept, fundamental DS
2	⭐⭐⭐⭐⭐	5. Two Pointers	★★☆☆☆	Array, String	Most common pattern
2	⭐⭐⭐⭐⭐	6. Sliding Window	★★★☆☆	Two Pointers	Subarray problems
2	⭐⭐⭐⭐☆	7. Stack	★★☆☆☆	Array	Parsing, matching, undo operations
2	⭐⭐⭐⭐☆	8. Queue	★★☆☆☆	Array, Stack	BFS, scheduling, buffering
2	⭐⭐⭐⭐⭐	9. Recursion	★★★☆☆	Stack (concept)	Required for Trees, DFS, DP
2	⭐⭐⭐⭐☆	10. Sorting	★★☆☆☆	Array, Recursion	Many problems need sorted data
3	⭐⭐⭐⭐⭐	11. Tree	★★★☆☆	Recursion, Queue	Most important interview topic
3	⭐⭐⭐⭐⭐	12. DFS	★★★☆☆	Tree, Recursion	Tree traversal, path finding
3	⭐⭐⭐⭐☆	13. BFS	★★★☆☆	Tree, Queue	Level order, shortest path
3	⭐⭐⭐⭐☆	14. Binary Search	★★★☆☆	Array, Sorting	O(log n) searching, very common
4	⭐⭐⭐☆☆	15. Heap/Priority Queue	★★★☆☆	Array, Tree	Kth problems, Dijkstra
4	⭐⭐⭐☆☆	16. Graph	★★★★☆	Tree, DFS, BFS	Advanced, but important for FAANG
4	⭐⭐⭐☆☆	17. Prefix Sum	★★☆☆☆	Array	Optimization technique
4	⭐⭐☆☆☆	18. Backtracking	★★★★☆	Recursion, DFS	Combinatorial problems
4	⭐⭐☆☆☆	19. Greedy	★★★★☆	Sorting, Recursion	Optimization, requires intuition
4	⭐☆☆☆☆	20. Dynamic Programming	★★★★★	ALL OF THE ABOVE	Hardest — save for last!

🎨 Priority Color Guide

• 🔵 Phase 1 — Must learn first: basic building blocks
• 🟢 Phase 2 — Core techniques: learn immediately after
• 🟡 Phase 3 — Interview favorites: most asked topics
• 🔴 Phase 4 — Advanced: learn after mastering the others

📏 Difficulty Guide

Stars	Meaning
★☆☆☆☆	Very Easy — Beginner friendly
★★☆☆☆	Easy — Basic understanding needed
★★★☆☆	Medium — Requires practice
★★★★☆	Hard — Needs strong fundamentals
★★★★★	Very Hard — Expert level

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🧩 Top 350 LeetCode Problems by Topic

Phase 1

Array (25 Problems)

#	Problem	Difficulty
1	Two Sum	Easy
26	Remove Duplicates from Sorted Array	Easy
27	Remove Element	Easy
35	Search Insert Position	Easy
53	Maximum Subarray	Easy
66	Plus One	Easy
88	Merge Sorted Array	Easy
118	Pascal's Triangle	Easy
119	Pascal's Triangle II	Easy
121	Best Time to Buy/Sell Stock	Easy
122	Best Time to Buy/Sell Stock II	Easy
136	Single Number	Easy
152	Maximum Product Subarray	Medium
153	Find Minimum in Rotated Array	Medium
169	Majority Element	Easy
189	Rotate Array	Medium
217	Contains Duplicate	Easy
219	Contains Duplicate II	Easy
238	Product of Array Except Self	Medium
268	Missing Number	Easy
283	Move Zeroes	Easy
303	Range Sum Query - Immutable	Easy
334	Increasing Triplet Subsequence	Medium
349	Intersection of Two Arrays	Easy
350	Intersection of Two Arrays II	Easy

String (20 Problems)

#	Problem	Difficulty
3	Longest Substring Without Repeating	Medium
5	Longest Palindromic Substring	Medium
6	Zigzag Conversion	Medium
8	String to Integer (atoi)	Medium
14	Longest Common Prefix	Easy
20	Valid Parentheses	Easy
28	Find the Index of First Occurrence	Easy
38	Count and Say	Medium
49	Group Anagrams	Medium
58	Length of Last Word	Easy
67	Add Binary	Easy
125	Valid Palindrome	Easy
151	Reverse Words in a String	Medium
165	Compare Version Numbers	Medium
205	Isomorphic Strings	Easy
242	Valid Anagram	Easy
290	Word Pattern	Easy
344	Reverse String	Easy
387	First Unique Character	Easy
415	Add Strings	Easy

Hash Table (15 Problems)

#	Problem	Difficulty
1	Two Sum	Easy
36	Valid Sudoku	Medium
49	Group Anagrams	Medium
128	Longest Consecutive Sequence	Medium
136	Single Number	Easy
138	Copy List with Random Pointer	Medium
141	Linked List Cycle	Easy
142	Linked List Cycle II	Medium
160	Intersection of Two Linked Lists	Easy
187	Repeated DNA Sequences	Medium
202	Happy Number	Easy
204	Count Primes	Medium
205	Isomorphic Strings	Easy
217	Contains Duplicate	Easy
219	Contains Duplicate II	Easy

Linked List (15 Problems)

#	Problem	Difficulty
2	Add Two Numbers	Medium
19	Remove Nth Node From End	Medium
21	Merge Two Sorted Lists	Easy
23	Merge k Sorted Lists	Hard
24	Swap Nodes in Pairs	Medium
25	Reverse Nodes in k-Group	Hard
61	Rotate List	Medium
82	Remove Duplicates from Sorted II	Medium
83	Remove Duplicates from Sorted	Easy
86	Partition List	Medium
92	Reverse Linked List II	Medium
138	Copy List with Random Pointer	Medium
141	Linked List Cycle	Easy
142	Linked List Cycle II	Medium
143	Reorder List	Medium
148	Sort List	Medium
160	Intersection of Two LL	Easy
203	Remove Linked List Elements	Easy
206	Reverse Linked List	Easy
234	Palindrome Linked List	Easy

Phase 2

Two Pointers (15 Problems)

#	Problem	Difficulty
3	Longest Substring Without Repeating	Medium
5	Longest Palindromic Substring	Medium
11	Container With Most Water	Medium
15	3Sum	Medium
16	3Sum Closest	Medium
18	4Sum	Medium
19	Remove Nth Node From End	Medium
26	Remove Duplicates from Sorted	Easy
27	Remove Element	Easy
28	Find the Index of First Occurrence	Easy
42	Trapping Rain Water	Hard
75	Sort Colors	Medium
88	Merge Sorted Array	Easy
125	Valid Palindrome	Easy
141	Linked List Cycle	Easy
142	Linked List Cycle II	Medium
167	Two Sum II - Input Array Sorted	Medium
283	Move Zeroes	Easy
344	Reverse String	Easy
345	Reverse Vowels of a String	Easy

Sliding Window (15 Problems)

#	Problem	Difficulty
3	Longest Substring Without Repeating	Medium
76	Minimum Window Substring	Hard
209	Minimum Size Subarray Sum	Medium
239	Sliding Window Maximum	Hard
424	Longest Repeating Character Repl.	Medium
438	Find All Anagrams in a String	Medium
480	Sliding Window Median	Hard
567	Permutation in String	Medium
713	Subarray Product Less Than K	Medium
1004	Max Consecutive Ones III	Medium
1208	Get Equal Substrings Within Budget	Medium
1493	Longest Subarray of 1's After Del	Medium
1695	Maximum Erasure Value	Medium
1838	Frequency of the Most Frequent	Medium
2024	Maximize Confusion of Exam	Medium

Stack (16 Problems)

#	Problem	Difficulty
20	Valid Parentheses	Easy
32	Longest Valid Parentheses	Hard
42	Trapping Rain Water	Hard
71	Simplify Path	Medium
84	Largest Rectangle in Histogram	Hard
94	Binary Tree Inorder Traversal	Easy
144	Binary Tree Preorder Traversal	Easy
145	Binary Tree Postorder Traversal	Easy
150	Evaluate Reverse Polish Notation	Medium
155	Min Stack	Easy
224	Basic Calculator	Hard
227	Basic Calculator II	Medium
394	Decode String	Medium
496	Next Greater Element I	Easy
503	Next Greater Element II	Medium
739	Daily Temperatures	Medium

Queue (9 Problems)

#	Problem	Difficulty
207	Course Schedule	Medium
210	Course Schedule II	Medium
225	Implement Stack using Queues	Easy
232	Implement Queue using Stacks	Easy
346	Moving Average from Data Stream	Easy
353	Design Snake Game	Medium
622	Design Circular Queue	Medium
641	Design Circular Deque	Medium
933	Number of Recent Calls	Easy

Recursion (10 Problems)

#	Problem	Difficulty
21	Merge Two Sorted Lists	Easy
50	Pow(x, n)	Medium
70	Climbing Stairs	Easy
77	Combinations	Medium
94	Binary Tree Inorder Traversal	Easy
104	Maximum Depth of Binary Tree	Easy
144	Binary Tree Preorder Traversal	Easy
145	Binary Tree Postorder Traversal	Easy
206	Reverse Linked List	Easy
509	Fibonacci Number	Easy

Sorting (10 Problems)

#	Problem	Difficulty
56	Merge Intervals	Medium
57	Insert Interval	Medium
75	Sort Colors	Medium
148	Sort List	Medium
164	Maximum Gap	Hard
215	Kth Largest Element in an Array	Medium
347	Top K Frequent Elements	Medium
451	Sort Characters By Frequency	Medium
912	Sort an Array	Medium
973	K Closest Points to Origin	Medium

Phase 3

Tree (20 Problems)

#	Problem	Difficulty
94	Binary Tree Inorder Traversal	Easy
98	Validate Binary Search Tree	Medium
100	Same Tree	Easy
101	Symmetric Tree	Easy
102	Binary Tree Level Order Traversal	Medium
103	Binary Tree Zigzag Level Order	Medium
104	Maximum Depth of Binary Tree	Easy
105	Construct from Preorder/Inorder	Medium
106	Construct from Inorder/Postorder	Medium
108	Convert Sorted Array to BST	Easy
110	Balanced Binary Tree	Easy
111	Minimum Depth of Binary Tree	Easy
112	Path Sum	Easy
113	Path Sum II	Medium
114	Flatten Binary Tree to Linked List	Medium
124	Binary Tree Maximum Path Sum	Hard
129	Sum Root to Leaf Numbers	Medium
144	Binary Tree Preorder Traversal	Easy
145	Binary Tree Postorder Traversal	Easy
173	Binary Search Tree Iterator	Medium
199	Binary Tree Right Side View	Medium
222	Count Complete Tree Nodes	Medium
226	Invert Binary Tree	Easy
230	Kth Smallest Element in BST	Medium
235	Lowest Common Ancestor of BST	Easy
236	Lowest Common Ancestor of BT	Medium
337	House Robber III	Medium
437	Path Sum III	Medium
543	Diameter of Binary Tree	Easy
572	Subtree of Another Tree	Easy

DFS (10 Problems)

#	Problem	Difficulty
17	Letter Combinations Phone Number	Medium
22	Generate Parentheses	Medium
39	Combination Sum	Medium
40	Combination Sum II	Medium
46	Permutations	Medium
47	Permutations II	Medium
78	Subsets	Medium
79	Word Search	Medium
90	Subsets II	Medium
200	Number of Islands	Medium

BFS (10 Problems)

#	Problem	Difficulty
102	Binary Tree Level Order Traversal	Medium
107	Binary Tree Level Order Traversal II	Medium
127	Word Ladder	Hard
133	Clone Graph	Medium
207	Course Schedule	Medium
210	Course Schedule II	Medium
279	Perfect Squares	Medium
322	Coin Change	Medium
542	01 Matrix	Medium
994	Rotting Oranges	Medium

Binary Search (15 Problems)

#	Problem	Difficulty
33	Search in Rotated Sorted Array	Medium
34	Find First and Last Position	Medium
35	Search Insert Position	Easy
50	Pow(x, n)	Medium
69	Sqrt(x)	Easy
74	Search a 2D Matrix	Medium
81	Search in Rotated Sorted Array II	Medium
153	Find Minimum in Rotated Array	Medium
154	Find Minimum in Rotated Array II	Hard
162	Find Peak Element	Medium
240	Search a 2D Matrix II	Medium
278	First Bad Version	Easy
367	Valid Perfect Square	Easy
378	Kth Smallest in Sorted Matrix	Medium
410	Split Array Largest Sum	Hard

Phase 4

Heap / Priority Queue (13 Problems)

#	Problem	Difficulty
23	Merge k Sorted Lists	Hard
215	Kth Largest Element in Array	Medium
239	Sliding Window Maximum	Hard
253	Meeting Rooms II	Medium
295	Find Median from Data Stream	Hard
347	Top K Frequent Elements	Medium
358	Rearrange String k Distance Apart	Hard
373	Find K Pairs with Smallest Sums	Medium
378	Kth Smallest in Sorted Matrix	Medium
692	Top K Frequent Words	Medium
703	Kth Largest Element in Stream	Easy
767	Reorganize String	Medium
973	K Closest Points to Origin	Medium

Graph (15 Problems)

#	Problem	Difficulty
133	Clone Graph	Medium
200	Number of Islands	Medium
207	Course Schedule	Medium
210	Course Schedule II	Medium
261	Graph Valid Tree	Medium
323	Number of Connected Components	Medium
329	Longest Increasing Path Matrix	Hard
332	Reconstruct Itinerary	Hard
399	Evaluate Division	Medium
547	Number of Provinces	Medium
684	Redundant Connection	Medium
785	Is Graph Bipartite?	Medium
797	All Paths From Source to Target	Medium
841	Keys and Rooms	Medium
886	Possible Bipartition	Medium

Prefix Sum (10 Problems)

#	Problem	Difficulty
53	Maximum Subarray	Easy
209	Minimum Size Subarray Sum	Medium
238	Product of Array Except Self	Medium
303	Range Sum Query - Immutable	Easy
304	Range Sum Query 2D - Immutable	Medium
437	Path Sum III	Medium
523	Continuous Subarray Sum	Medium
560	Subarray Sum Equals K	Medium
724	Find Pivot Index	Easy
930	Binary Subarrays With Sum	Medium

Backtracking (15 Problems)

#	Problem	Difficulty
17	Letter Combinations Phone Number	Medium
22	Generate Parentheses	Medium
37	Sudoku Solver	Hard
39	Combination Sum	Medium
40	Combination Sum II	Medium
46	Permutations	Medium
47	Permutations II	Medium
51	N-Queens	Hard
52	N-Queens II	Hard
77	Combinations	Medium
78	Subsets	Medium
79	Word Search	Medium
90	Subsets II	Medium
93	Restore IP Addresses	Medium
131	Palindrome Partitioning	Medium

Greedy (12 Problems)

#	Problem	Difficulty
45	Jump Game II	Medium
55	Jump Game	Medium
122	Best Time to Buy/Sell Stock II	Medium
134	Gas Station	Medium
135	Candy	Hard
376	Wiggle Subsequence	Medium
406	Queue Reconstruction by Height	Medium
435	Non-overlapping Intervals	Medium
452	Minimum Number of Arrows Burst	Medium
455	Assign Cookies	Easy
621	Task Scheduler	Medium
763	Partition Labels	Medium

Dynamic Programming (60 Problems)

#	Problem	Difficulty
5	Longest Palindromic Substring	Medium
10	Regular Expression Matching	Hard
22	Generate Parentheses	Medium
32	Longest Valid Parentheses	Hard
44	Wildcard Matching	Hard
53	Maximum Subarray	Easy
62	Unique Paths	Medium
63	Unique Paths II	Medium
64	Minimum Path Sum	Medium
70	Climbing Stairs	Easy
72	Edit Distance	Hard
91	Decode Ways	Medium
96	Unique Binary Search Trees	Medium
97	Interleaving String	Hard
115	Distinct Subsequences	Hard
118	Pascal's Triangle	Easy
119	Pascal's Triangle II	Easy
120	Triangle	Medium
121	Best Time to Buy/Sell Stock	Easy
122	Best Time to Buy/Sell Stock II	Medium
123	Best Time to Buy/Sell Stock III	Hard
124	Binary Tree Maximum Path Sum	Hard
139	Word Break	Medium
140	Word Break II	Hard
152	Maximum Product Subarray	Medium
198	House Robber	Medium
213	House Robber II	Medium
221	Maximal Square	Medium
279	Perfect Squares	Medium
300	Longest Increasing Subsequence	Medium
309	Best Time to Buy/Sell Stock Cooldown	Medium
322	Coin Change	Medium
329	Longest Increasing Path Matrix	Hard
337	House Robber III	Medium
338	Counting Bits	Easy
416	Partition Equal Subset Sum	Medium
494	Target Sum	Medium
516	Longest Palindromic Subsequence	Medium
518	Coin Change II	Medium
583	Delete Operation for Two Strings	Medium
647	Palindromic Substrings	Medium
673	Number of Longest Inc Subsequence	Medium
674	Longest Continuous Inc Subseq	Easy
712	Minimum ASCII Delete Sum	Medium
718	Maximum Length of Repeated Subarray	Medium
746	Min Cost Climbing Stairs	Easy
790	Domino and Tromino Tiling	Medium
873	Length of Longest Fibonacci Subseq	Medium
978	Longest Turbulent Subarray	Medium
1043	Partition Array for Max Sum	Medium
1048	Longest String Chain	Medium
1049	Last Stone Weight II	Medium
1105	Filling Bookcase Shelves	Medium
1130	Minimum Cost Tree From Leaf	Medium
1143	Longest Common Subsequence	Medium
1155	Number of Dice Rolls Target	Medium
1220	Count Vowels Permutation	Hard
1235	Maximum Profit Job Scheduling	Hard
1262	Greatest Sum Divisible by Three	Medium
1335	Minimum Difficulty Job Schedule	Hard

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📊 Summary

Metric	Count
Total Problems	350
Easy	75+
Medium	200+
Hard	75+

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🎯 Recommended Interview Prep — Top 100

If you're short on time, focus on these problem numbers (by phase):

Phase 1 (30 problems)

1, 21, 26, 49, 53, 56, 88, 94, 100, 101, 102, 104, 121, 125, 136, 141, 144,
145, 155, 169, 200, 206, 217, 226, 230, 234, 238, 242, 283, 344

Phase 2 (30 problems)

3, 5, 11, 15, 17, 19, 20, 22, 33, 34, 39, 42, 46, 70, 75, 78, 79, 98, 105,
108, 110, 112, 124, 133, 139, 146, 150, 207, 215, 322

Phase 3 (25 problems)

23, 32, 37, 45, 51, 55, 62, 72, 76, 91, 114, 127, 128, 131, 138, 139, 148,
152, 153, 198, 200, 207, 215, 237, 239

Phase 4 (15 problems)

10, 37, 42, 44, 51, 72, 84, 124, 127, 140, 212, 295, 312, 329, 410

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✅ How to Use This Roadmap

1. Work through Phase 1 → Phase 4 in order — each phase builds on the last.
2. Within each topic, solve Easy → Medium → Hard.
3. Save Dynamic Programming for last — it depends on nearly everything else.
4. Use the Top 100 list above if you're prepping under time pressure.