🎯 DSA Master Learning Plan - Pattern by Pattern

Source: Dev.to

My Story

Like many developers, I’ve been putting off learning DSA for months. I don’t have endless hours to dedicate, and the traditional “solve 1000 problems” approach felt overwhelming.
So I did something different—I used AI to build a custom learning plan that fits my schedule and learning style. This isn’t another generic DSA roadmap; it’s a stress‑free, pattern‑focused approach that prioritizes depth over breadth.

I spent time with Claude AI to:

• Break down DSA into digestible patterns
• Order them from foundational to advanced
• Select 10‑15 problems per pattern (not 100!)
• Build in revision cycles so I don’t forget
• Make it flexible—no rigid daily schedules

The philosophy is simple: master one pattern deeply before moving to the next.

Philosophy

Master one pattern at a time.
Solve 10+ problems per pattern before moving on.

Timeline

1 year to become a DSA master (stress‑free!).

Revision

Every fortnight, solve 2‑3 problems from already mastered patterns.

Phase 1: Foundation (Weeks 1‑8)

These patterns build your fundamental problem‑solving skills.

Pattern 1: Array Basics

Goal: Understand array traversal and basic operations.

Problems to master (10‑12):

• 217. Contains Duplicate – Easy warm‑up
• 169. Majority Element – Boyer‑Moore voting
• 189. Rotate Array – Reversal technique
• 41. First Missing Positive – Index as hash
• 442. Find All Duplicates in an Array
• 448. Find All Numbers Disappeared in an Array
• 287. Find the Duplicate Number
• 243. Shortest Word Distance
• 849. Maximize Distance to Closest Person
• 384. Shuffle an Array – Fisher‑Yates

C# data structures used: int[], List, HashSet

Pattern 2: Two Pointers – Same Direction

Goal: Use two pointers moving in the same direction.

Problems to master (10‑12):

• 283. Move Zeroes – Classic starter
• 27. Remove Element
• 26. Remove Duplicates from Sorted Array
• 80. Remove Duplicates from Sorted Array II
• 75. Sort Colors – Dutch National Flag
• 121. Best Time to Buy and Sell Stock
• 122. Best Time to Buy and Sell Stock II
• 31. Next Permutation
• 556. Next Greater Element III
• 165. Compare Version Numbers
• 1574. Shortest Subarray to be Removed to Make Array Sorted

C# skills: index manipulation, while loops with two indices.

Pattern 3: Two Pointers – Opposite Direction

Goal: Pointers moving from both ends toward the center.

Problems to master (10‑12):

• 125. Valid Palindrome – Start here
• 344. Reverse String
• 680. Valid Palindrome II
• 167. Two Sum II – Input Array Is Sorted
• 15. 3Sum – Important pattern
• 16. 3Sum Closest
• 18. 4Sum
• 977. Squares of a Sorted Array
• 11. Container With Most Water – Classic
• 42. Trapping Rain Water – Must master
• 5. Longest Palindromic Substring

Key algorithm: expand‑around‑center technique.

Pattern 4: Sliding Window – Fixed Size

Goal: Maintain a window of fixed size.

Problems to master (6‑8):

• 1100. Find K‑Length Substrings With No Repeated Characters
• 1151. Minimum Swaps to Group All 1’s Together
• 2134. Minimum Swaps to Group All 1’s Together II
• 1423. Maximum Points You Can Obtain from Cards
• 187. Repeated DNA Sequences
• 346. Moving Average from Data Stream

C# data structures: Queue, Dictionary

Pattern 5: Sliding Window – Variable Size

Goal: Shrink/expand window based on a condition.

Problems to master (10‑12):

• 3. Longest Substring Without Repeating Characters – Must know
• 209. Minimum Size Subarray Sum
• 340. Longest Substring with At Most K Distinct Characters
• 904. Fruit Into Baskets
• 424. Longest Repeating Character Replacement
• 567. Permutation in String
• 438. Find All Anagrams in a String
• 76. Minimum Window Substring – Hard but essential
• 30. Substring with Concatenation of All Words
• 395. Longest Substring with At Least K Repeating Characters

This is the most important pattern for interviews.

Pattern 6: HashMap / HashSet

Goal: O(1) lookups for efficiency.

Problems to master (12‑15):

• 1. Two Sum – Classic starter
• 242. Valid Anagram
• 383. Ransom Note
• 387. First Unique Character in a String
• 49. Group Anagrams
• 128. Longest Consecutive Sequence
• 205. Isomorphic Strings
• 409. Longest Palindrome
• 953. Verifying an Alien Dictionary
• 380. Insert Delete GetRandom O(1)
• 1010. Pairs of Songs With Total Durations Divisible by 60
• 299. Bulls and Cows

C# data structures: Dictionary, HashSet

Phase 2: Intermediate Patterns (Weeks 9‑20)

Pattern 7: Prefix Sum

Goal: Pre‑compute cumulative sums for range queries.

Problems to master (10‑12):

• 303. Range Sum Query – Immutable – Start here
• 304. Range Sum Query 2D – Immutable
• 238. Product of Array Except Self
• 724. Find Pivot Index
• 560. Subarray Sum Equals K – Important
• 525. Contiguous Array
• 523. Continuous Subarray Sum
• 974. Subarray Sums Divisible by K
• 1248. Count Number of Nice Subarrays
• 1031. Maximum Sum of Two Non‑Overlapping Subarrays

Key technique: use a HashMap to store prefix sums.

Pattern 8: Stack / Queue

Goal: Master LIFO and FIFO operations.

Problems to master (10‑12):

• 20. Valid Parentheses – Must know
• 155. Min Stack
• 150. Evaluate Reverse Polish Notation
• 224. Basic Calculator
• 227. Basic Calculator II
• 394. Decode String
• 71. Simplify Path
• 1249. Minimum Remove to Make Valid Parentheses
• 232. Implement Queue using Stacks
• 225. Implement Stack using Queues

C# data structures: Stack, Queue

Pattern 9: Monotonic Stack / Queue

Goal: Maintain increasing/decreasing order.

Problems to master (8‑10):

• 739. Daily Temperatures – Start here
• 496. Next Greater Element I
• 503. Next Greater Element II
• 402. Remove K Digits
• 239. Sliding Window Maximum – Classic
• 1438. Longest Continuous Subarray With Absolute Diff ≤ Limit
• 862. Shortest Subarray with Sum at Least K

This pattern is a game‑changer for optimization!

Pattern 10: Binary Search

Goal: O(log n) search in sorted spaces.

Problems to master (12‑15):

• 704. Binary Search – Template
• 35. Search Insert Position
• 34. Find First and Last Position of Element in Sorted Array
• 74. Search a 2D Matrix
• 33. Search in Rotated Sorted Array
• 153. Find Minimum in Rotated Sorted Array
• 162. Find Peak Element
• 278. First Bad Version
• 875. Koko Eating Bananas – Binary search on answer
• 1011. Capacity To Ship Packages Within D Days
• 4. Median of Two Sorted Arrays – Hard
• 981. Time Based Key‑Value Store

Learn the template pattern first!

Pattern 11: Intervals / Line Sweep

Goal: Merge, intersect, and manage intervals.

Problems to master (10‑12):

• 252. Meeting Rooms – Easy start
• 56. Merge Intervals – Must know
• 57. Insert Interval
• 435. Non‑overlapping Intervals
• 986. Interval List Intersections
• 253. Meeting Rooms II – Use heap
• 452. Minimum Number of Arrows to Burst Balloons
• 1288. Remove Covered Intervals
• 1229. Meeting Scheduler
• 1272. Remove Interval

C# technique: Array.Sort(intervals, (a, b) => a[0].CompareTo(b[0]))

Phase 3: Advanced Patterns (Weeks 21‑35)

Pattern 12: Linked List

Goal: Master pointer manipulation.

Problems to master (12‑15):

• 206. Reverse Linked List – Must know
• 21. Merge Two Sorted Lists
• 141. Linked List Cycle
• 142. (continue with additional linked‑list problems as needed)

Further advanced patterns can be added following the same structure.