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C Codeloom

Roadmap

Roadmap to becoming an SDE.

Every DSA topic is its own dropdown — Arrays, Hashing, Trees, Graphs, DP, and more. Inside each topic you get Articles (our written tutorials), Questions (curated LeetCode problems with solution write-ups), and References.

📘 Article 🧭 Topic page 🟧 LeetCode 🟩 GeeksforGeeks

🌱Programming Foundations [Python, Java, C++, OOP, Git]

Before any DSA, you need to write code comfortably in one language.

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⏱️Time & Space Complexity [Big-O, Analysis]

Learn to estimate cost before writing code.

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🔁Recursion [Base case, Stack frames]

Recursion underlies trees, graphs, backtracking, and DP.

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📦Arrays [Prefix Sum, Kadane, Rotation]

The most-asked category in interviews. Start here.

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🧩 Questions

Problem Solution LeetCode GFG Difficulty
Two Sum Read → Solve ↗ Read ↗ Easy
Product of Array Except Self Read → Solve ↗ Medium
Maximum Subarray (Kadane) Read → Solve ↗ Medium
Rotate Array Read → Medium
Maximum Product Subarray Read → Medium
Jump Game Read → Medium
Merge Intervals Read → Medium

🔑Hashing [Hash Maps, Frequency, Sets]

Frequency counting, lookup tables, deduping.

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🧩 Questions

Problem Solution LeetCode GFG Difficulty
Valid Anagram Read → Solve ↗ Easy
Group Anagrams Read → Solve ↗ Medium
Top K Frequent Elements Read → Solve ↗ Medium
Longest Consecutive Sequence Read → Solve ↗ Medium

🎯Two Pointers [Sorted Arrays, Opposite Ends]

Opposite-end pointers for sorted-array problems.

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🧩 Questions

Problem Solution LeetCode GFG Difficulty
3Sum Read → Solve ↗ Read ↗ Medium
Container With Most Water Read → Solve ↗ Medium
Trapping Rain Water Read → Solve ↗ Hard

🪟Sliding Window [Fixed Window, Variable Window]

Window patterns for substring / subarray problems.

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🧩 Questions

Problem Solution LeetCode GFG Difficulty
Best Time to Buy and Sell Stock Read → Solve ↗ Easy
Longest Substring Without Repeating Characters Read → Solve ↗ Medium
Sliding Window Maximum Read → Solve ↗ Hard

🔤Strings [Palindromes, Anagrams, Encoding]

Palindromes, anagrams, encoding/decoding.

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🧩 Questions

Problem Solution LeetCode GFG Difficulty
Longest Palindromic Substring Read → Solve ↗ Medium
Palindrome Number Read → Easy
Reverse String Read → Easy

🔗 References

🥞Stacks and Queues [Monotonic Stack, Pre-In-Post-fix, Implementation]

Monotonic stacks, parenthesis matching, expression evaluation.

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🧩 Questions

Problem Solution LeetCode GFG Difficulty
Valid Parentheses Read → Solve ↗ Easy
Min Stack Read → Solve ↗ Medium
Daily Temperatures Read → Solve ↗ Medium

🔗Linked Lists [Singly, Doubly, Fast/Slow]

Single/double lists, dummy nodes, fast/slow pointers.

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🧩 Questions

Problem Solution LeetCode GFG Difficulty
Reverse Linked List Read → Solve ↗ Easy
Merge Two Sorted Lists Read → Solve ↗ Easy
LRU Cache Read → Solve ↗ Medium

🔎Binary Search [Sorted, Rotated, Answer Space]

Logarithmic thinking. Sorted, rotated, or "answer-space" arrays.

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🧩 Questions

Problem Solution LeetCode GFG Difficulty
Search in Rotated Sorted Array Read → Solve ↗ Medium
Find Minimum in Rotated Sorted Array Read → Medium

📊Sorting [Merge, Quick, Heap]

Merge, quick, heap. Know when to pick each.

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🧩 Questions

Problem Solution LeetCode GFG Difficulty
Rotate Image Read → Medium
Spiral Matrix Read → Medium

🔗 References

⛰️Heaps [Min-Heap, Max-Heap, Top-K]

Priority queues for top-K, scheduling, and streaming problems.

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🧩 Questions

Problem Solution LeetCode GFG Difficulty
Find Median from Data Stream Read → Hard
Meeting Rooms II Read → Medium

💡Greedy Algorithms [Easy, Medium, Hard]

Take the locally best choice — prove it leads to the global optimum.

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🧩 Questions

Problem Solution LeetCode GFG Difficulty
Jump Game Read → Medium
Merge Intervals Read → Medium

🌳Binary Trees [Traversals, Medium, Hard]

Traversals, depth, validation, LCA.

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🧩 Questions

Problem Solution LeetCode GFG Difficulty
Invert Binary Tree Read → Solve ↗ Easy
Maximum Depth of Binary Tree Read → Solve ↗ Easy
Binary Tree Level Order Traversal Read → Solve ↗ Medium
Validate Binary Search Tree Read → Solve ↗ Medium
Kth Smallest Element in BST Read → Medium
Lowest Common Ancestor of BST Read → Medium
Path Sum Read → Easy
Serialize and Deserialize Binary Tree Read → Hard

🔗 References

🕸️Graphs [BFS, DFS, Topo Sort, Union-Find]

Adjacency lists, BFS/DFS, topological sort, union-find.

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🧩 Questions

Problem Solution LeetCode GFG Difficulty
Number of Islands Read → Solve ↗ Medium
Clone Graph Read → Solve ↗ Medium
Course Schedule Read → Solve ↗ Medium
Pacific Atlantic Water Flow Read → Medium
Word Ladder Read → Hard

🔗 References

🌀Backtracking [Subsets, Permutations, Combinations]

Recursive search with undo. The "choose / explore / unchoose" template.

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🧩 Questions

Problem Solution LeetCode GFG Difficulty
Subsets Read → Solve ↗ Medium
Permutations Read → Solve ↗ Medium
Combination Sum Read → Medium
Generate Parentheses Read → Medium
Letter Combinations of a Phone Number Read → Medium

🧠Dynamic Programming [1D, 2D, Memoize, Tabulate]

The hardest interview category. Memoize first, then tabulate.

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🧩 Questions

Problem Solution LeetCode GFG Difficulty
Climbing Stairs Read → Solve ↗ Easy
House Robber Read → Solve ↗ Medium
Word Break Read → Solve ↗ Medium
Coin Change Read → Medium
Longest Increasing Subsequence Read → Medium
Unique Paths Read → Medium
Edit Distance Read → Hard

🗃️Databases & SQL [SELECT, JOIN, Indexes]

Asked in nearly every backend interview.

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🏗️System Design [HTTP, Caching, Queues, Load Balancers]

HTTP, REST, caching, queues, load balancers, databases.

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📝Resume, Behavioral & Negotiation [Resume, STAR, Offer]

The non-coding parts of the interview that decide compensation.

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Ready to apply?

Once you can solve mediums fluently, pair this roadmap with our resume, behavioral, and negotiation guides.