Master Problem Index & Tracker
—
Solved by you
205
Total problems
—
Overall progress
What & why: every canonical problem in this book, in one checkable list — grouped by pattern/chapter, with difficulty and a direct LeetCode link. Use it as a coverage map and a progress tracker: tick the box each time you can reproduce a solution cold. Chapter titles link back to the full write-up.
How to use this tracker
don't grind top-to-bottom. Follow the study plan: learn a pattern's card, then drill its rows here. Re-touch on the spaced-repetition schedule. A row isn't "done" when you've seen it — it's done when you can re-derive the invariant and code the template from the name alone.
Legend: ☐ = not yet reproducible cold · Easy Medium Hard · 91 canonical problems across 18 pattern areas. Technique-only sections (e.g. tree traversals, KMP, k-way merge, modular arithmetic) are taught in-chapter and not double-listed here.
Arrays & Hashing
| ✓ | Problem | Difficulty | LeetCode |
|---|---|---|---|
| ☐ | Two Sum | Easy | open |
| ☐ | Group Anagrams | Medium | open |
| ☐ | Product of Array Except Self | Medium | open |
| ☐ | Longest Consecutive Sequence | Medium | open |
| ☐ | Rotate Image | Medium | open |
| ☐ | Spiral Matrix | Medium | open |
| ☐ | Set Matrix Zeroes | Medium | open |
Prefix Sum
| ✓ | Problem | Difficulty | LeetCode |
|---|---|---|---|
| ☐ | Subarray Sum Equals K | Medium | open |
| ☐ | Difference Array | Medium | open |
| ☐ | 2D Prefix Sum | Medium | open |
Two Pointers / Sliding Window
| ✓ | Problem | Difficulty | LeetCode |
|---|---|---|---|
| ☐ | 3Sum | Medium | open |
| ☐ | Container With Most Water | Medium | open |
| ☐ | Squaring a Sorted Array | Easy | open |
| ☐ | Sort Colors | Medium | open |
| ☐ | Trapping Rain Water | Hard | open |
| ☐ | Smallest Subarray With Sum ≥ Target | Medium | open |
| ☐ | Longest Substring Without Repeating Characters | Medium | open |
| ☐ | Minimum Window Substring | Hard | open |
| ☐ | Longest Repeating Character Replacement | Medium | open |
| ☐ | Sliding Window Maximum | Hard | open |
Cyclic Sort
| ✓ | Problem | Difficulty | LeetCode |
|---|---|---|---|
| ☐ | Find the Missing Number | Easy | open |
| ☐ | Find All Missing / All Duplicate Numbers | Medium | open |
| ☐ | First Missing Positive | Hard | open |
Stacks & Monotonic Stack
| ✓ | Problem | Difficulty | LeetCode |
|---|---|---|---|
| ☐ | Valid Parentheses | Easy | open |
| ☐ | Daily Temperatures | Medium | open |
| ☐ | Largest Rectangle in Histogram | Hard | open |
| ☐ | Min Stack (O(1) minimum) | Medium | open |
Binary Search & Greedy
| ✓ | Problem | Difficulty | LeetCode |
|---|---|---|---|
| ☐ | Search in Rotated Sorted Array | Medium | open |
| ☐ | Koko Eating Bananas | Medium | open |
| ☐ | Split Array Largest Sum / Book Allocation | Hard | open |
| ☐ | Median of Two Sorted Arrays | Hard | open |
| ☐ | Jump Game II | Medium | open |
| ☐ | Gas Station | Medium | open |
| ☐ | Task Scheduler / Activity Selection | Medium | open |
Intervals & Sweep Line
| ✓ | Problem | Difficulty | LeetCode |
|---|---|---|---|
| ☐ | Merge Intervals | Medium | open |
| ☐ | Meeting Rooms II | Medium | open |
| ☐ | Non-overlapping Intervals | Medium | open |
Backtracking & Divide-Conquer
| ✓ | Problem | Difficulty | LeetCode |
|---|---|---|---|
| ☐ | Subsets & Combinations | Medium | open |
| ☐ | Permutations | Medium | open |
| ☐ | Combination Sum | Medium | open |
| ☐ | N-Queens | Hard | open |
| ☐ | Word Search | Medium | open |
| ☐ | Merge Sort & Count of Smaller Numbers After Self | Hard | open |
| ☐ | Quickselect | Medium | open |
Dynamic Programming
| ✓ | Problem | Difficulty | LeetCode |
|---|---|---|---|
| ☐ | House Robber (1D DP) | Medium | open |
| ☐ | Maximum Subarray (Kadane) | Medium | open |
| ☐ | Partition Equal Subset Sum (Knapsack) | Medium | open |
| ☐ | Coin Change | Medium | open |
| ☐ | Unique Paths / Min Path Sum (Grid DP) | Medium | open |
| ☐ | LIS / LCS / Edit Distance (Subsequence DP) | Medium | open |
| ☐ | Burst Balloons (Interval DP) | Hard | open |
| ☐ | Stock with Cooldown (State-Machine DP) | Medium | open |
| ☐ | Travelling Salesman (Bitmask DP) | Hard | open |
Bits, Segment & Fenwick Tree
| ✓ | Problem | Difficulty | LeetCode |
|---|---|---|---|
| ☐ | Single Number I / II / III | Easy | open |
| ☐ | Counting Bits | Easy | open |
| ☐ | Subset Generation via Bitmasks | Medium | open |
| ☐ | Fenwick Tree | Medium | open |
| ☐ | Segment Tree | Hard | open |
Math & Number Theory
| ✓ | Problem | Difficulty | LeetCode |
|---|---|---|---|
| ☐ | Fast Exponentiation — Pow(x, n) | Medium | open |
| ☐ | Euclid's GCD & LCM — GCD of Strings | Easy | open |
| ☐ | Sieve of Eratosthenes — Count Primes | Medium | open |
Design & Randomized
| ✓ | Problem | Difficulty | LeetCode |
|---|---|---|---|
| ☐ | Insert Delete GetRandom O(1) | Medium | open |
| ☐ | Reservoir Sampling — Random Node | Medium | open |
Strings
| ✓ | Problem | Difficulty | LeetCode |
|---|---|---|---|
| ☐ | Longest Palindromic Substring | Medium | open |
| ☐ | Encode and Decode Strings | Medium | open |
Linked Lists
| ✓ | Problem | Difficulty | LeetCode |
|---|---|---|---|
| ☐ | Reverse a Linked List | Easy | open |
| ☐ | Linked List Cycle II | Medium | open |
| ☐ | Merge Two / K Sorted Lists | Hard | open |
| ☐ | Reorder / Palindrome via Split-Reverse-Merge | Medium | open |
| ☐ | LRU Cache | Medium | open |
Trees
| ✓ | Problem | Difficulty | LeetCode |
|---|---|---|---|
| ☐ | Maximum Depth, Balanced, Diameter | Medium | open |
| ☐ | Lowest Common Ancestor | Medium | open |
| ☐ | Validate BST & BST operations | Medium | open |
| ☐ | Serialize / Deserialize | Hard | open |
| ☐ | Construct Tree from Traversals | Medium | open |
| ☐ | Tree DP | Medium | open |
Heaps
| ✓ | Problem | Difficulty | LeetCode |
|---|---|---|---|
| ☐ | Kth Largest / Top K Frequent | Medium | open |
| ☐ | Find Median from Data Stream | Hard | open |
Tries
| ✓ | Problem | Difficulty | LeetCode |
|---|---|---|---|
| ☐ | Implement Trie | Medium | open |
| ☐ | Word Search II | Hard | open |
| ☐ | Maximum XOR of Two Numbers | Medium | open |
Graphs
| ✓ | Problem | Difficulty | LeetCode |
|---|---|---|---|
| ☐ | Number of Islands | Medium | open |
| ☐ | Rotting Oranges | Medium | open |
| ☐ | Course Schedule | Medium | open |
| ☐ | Network Delay Time (Dijkstra) | Medium | open |
| ☐ | Cheapest Flights K Stops (Bellman-Ford) | Medium | open |
| ☐ | Min Cost to Connect Points (MST) | Medium | open |
| ☐ | Number of Provinces (Union-Find) | Medium | open |
| ☐ | Clone Graph & Bipartite | Medium | open |
| ☐ | Bridges & Articulation Points (Tarjan) | Hard | open |
| ☐ | Eulerian Path (Hierholzer) | Hard | open |