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Leetcode Patterns Roadmap

Product-Based DSA Roadmap: Pattern Mastery

How to use: Focus on ONE pattern at a time. Do not move to the next pattern until you can solve the current pattern's problems without looking at the solution.

Phase 1: The Essentials (Arrays & Strings)

Pattern Problem Name Difficulty Link
Two Pointers
Sorted arrays, Pairs		 Valid Palindrome Easy Solve
Squares of a Sorted Array Easy Solve
Two Sum II - Input Array Is Sorted Medium Solve
Container With Most Water Medium Solve
3Sum Medium Solve
Trapping Rain Water Hard Solve
Sliding Window
Subarrays, Substrings		 Best Time to Buy and Sell Stock Easy Solve
Maximum Average Subarray I Easy Solve
Longest Substring Without Repeating Characters Medium Solve
Longest Repeating Character Replacement Medium Solve
Minimum Window Substring Hard Solve
Prefix Sum
Range sums		 Product of Array Except Self Medium Solve
Subarray Sum Equals K Medium Solve
Continuous Subarray Sum Medium Solve

Phase 2: Hashing & Linked Lists

Pattern Problem Name Difficulty Link
Hash Maps / Sets
Frequency, Lookups		 Two Sum Easy Solve
Valid Anagram Easy Solve
Group Anagrams Medium Solve
Longest Consecutive Sequence Medium Solve
Fast & Slow Pointers
Cycles, Middle finding		 Linked List Cycle Easy Solve
Middle of the Linked List Easy Solve
Find the Duplicate Number Medium Solve
Happy Number Easy Solve

Phase 3: Standard Data Structures

Pattern Problem Name Difficulty Link
Binary Search
Sorted, Rotated		 Binary Search Easy Solve
Search in Rotated Sorted Array Medium Solve
Find Minimum in Rotated Sorted Array Medium Solve
Koko Eating Bananas Medium Solve
Monotonic Stack
Next greater/smaller		 Next Greater Element I Easy Solve
Daily Temperatures Medium Solve
Largest Rectangle in Histogram Hard Solve
Intervals
Merge, Overlap		 Merge Intervals Medium Solve
Insert Interval Medium Solve
Non-overlapping Intervals Medium Solve

Phase 4: Trees, Graphs & Heaps

Pattern Problem Name Difficulty Link
BFS / DFS (Trees)
Level order, Depth		 Maximum Depth of Binary Tree Easy Solve
Invert Binary Tree Easy Solve
Binary Tree Level Order Traversal Medium Solve
Kth Smallest Element in a BST Medium Solve
Graphs
Islands, Networks		 Number of Islands Medium Solve
Rotting Oranges Medium Solve
Clone Graph Medium Solve
Top 'K' (Heaps)
Priority Queue		 Kth Largest Element in an Array Medium Solve
K Closest Points to Origin Medium Solve
Find Median from Data Stream Hard Solve

Phase 5: Dynamic Programming

Pattern Problem Name Difficulty Link
1D DP
Subproblems		 Climbing Stairs Easy Solve
House Robber Medium Solve
Coin Change Medium Solve
Longest Increasing Subsequence Medium Solve
Backtracking
Permutations, Subsets		 Permutations Medium Solve
Subsets Medium Solve
Combination Sum Medium Solve

Next Step: Start Phase 1. Solve "Valid Palindrome" first!

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