Stage 1 · Code
LeetCode Patterns for Interviews
The 15 patterns that unlock 90% of coding interviews — recognise the pattern, reuse the template, and stop memorising 500 problems.
Prerequisite
Programming Foundations + DSA.
What this course leaves you with
- Recognise the recurring patterns behind interview problems
- Solve medium problems under time pressure
- Explain trade-offs clearly while coding
Why this stage matters — You can code well — now learn the collaboration tooling every team expects.
Progress
0 of 42 lessons complete. Progress is stored locally in your browser so you can pick the path back up later.
course completion
Arrays & Hashing
The bread and butter of every interview — frequency maps, prefix sums, and O(1) lookups.
- 01Hash Map FundamentalsTwo Sum, Group Anagrams, Top K Frequent — counting with maps.8 min
- 02Prefix SumSubarray Sum Equals K, Range Sum Query, Product of Array Except Self.8 min
- 03Sets & DeduplicationContains Duplicate, Longest Consecutive Sequence in O(n).6 min
- 04Sorting TricksCounting sort, bucket sort, and when O(n log n) is the answer.7 min
- 05Matrix TraversalSpiral Matrix, Rotate Image, Set Matrix Zeroes in place.8 min
- 06Timed Problem Set12 curated problems, Easy → Medium, 45-minute drill.10 min
Two Pointers & Sliding Window
Turn O(n²) brute force into O(n) by moving pointers with intent.
- 01Opposite-End PointersValid Palindrome, 3Sum, Container With Most Water.8 min
- 02Fast & Slow PointersCycle detection, middle of list, happy number.7 min
- 03Fixed-Size Sliding WindowMax Average Subarray, anagram checks in a stream.7 min
- 04Dynamic Sliding WindowLongest Substring Without Repeat, Minimum Window Substring.9 min
- 05The Universal Window TemplateOne shrink/grow skeleton that solves the whole family.6 min
- 06Timed Problem Set10 curated window/pointer problems under time pressure.10 min
Stack & Binary Search
Monotonic stacks and the search space you didn't know you could bisect.
- 01Monotonic StackDaily Temperatures, Next Greater Element, Largest Rectangle.9 min
- 02Stack for ParsingValid Parentheses, Decode String, evaluate RPN.7 min
- 03Classic Binary SearchBoundaries, off-by-one, and the lo/hi/mid invariants.8 min
- 04Binary Search on the AnswerKoko Eating Bananas, Split Array Largest Sum, capacity to ship.9 min
- 05Rotated & 2D SearchSearch in Rotated Sorted Array, search a 2D matrix.7 min
- 06Timed Problem Set10 problems mixing stacks and binary search.10 min
Linked Lists & Trees
Pointer surgery and recursive thinking — the backbone of Medium interviews.
- 01Linked List ManipulationReverse, merge, reorder, and remove Nth from end.8 min
- 02Tree TraversalsDFS/BFS, pre/in/post order, iterative and recursive.8 min
- 03Binary Search TreesValidate BST, kth smallest, lowest common ancestor.8 min
- 04Tree Construction & PathsBuild from traversals, diameter, path sum, serialize/deserialize.9 min
- 05Tries & Prefix TreesImplement Trie, word search II, autocomplete.7 min
- 06Timed Problem Set12 tree/list problems, Medium-weighted.10 min
Graphs & Backtracking
Model the problem as a graph, then search it — BFS, DFS, union-find, and choose/explore/unchoose.
- 01Graph Representations & TraversalAdjacency lists, BFS/DFS on grids and nodes.8 min
- 02Topological SortCourse Schedule, alien dictionary, cycle detection.8 min
- 03Union-FindNumber of Provinces, redundant connection, accounts merge.8 min
- 04Shortest Path & DijkstraNetwork delay, cheapest flights, BFS on weighted grids.9 min
- 05The Backtracking TemplateSubsets, permutations, combination sum, N-Queens.9 min
- 06Timed Problem Set10 graph/backtracking problems, Medium → Hard.10 min
Dynamic Programming & Greedy
The feared round, demystified — recognise overlapping subproblems and define the state.
- 011-D DPClimbing Stairs, House Robber, decode ways.8 min
- 022-D DPUnique Paths, edit distance, longest common subsequence.9 min
- 03Knapsack Family0/1 knapsack, coin change, partition equal subset.9 min
- 04DP on Strings & IntervalsPalindromic substrings, burst balloons, matrix chain.9 min
- 05Greedy & IntervalsJump Game, merge intervals, task scheduler, gas station.8 min
- 06Timed Problem Set12 DP/greedy problems with state-definition hints.10 min
Mock Interviews & Strategy
Bring it together — communication, complexity analysis, and the 45-minute loop.
- 01Clarify, Plan, CommunicateThe UMPIRE method and thinking out loud without freezing.6 min
- 02Complexity On DemandDeriving time/space live and spotting the bottleneck.7 min
- 03Blind 75 RoadmapA 6-week schedule mapping every pattern to problems.8 min
- 04Mock Loop: ScreeningTwo timed problems as a phone-screen simulation.12 min
- 05Mock Loop: OnsiteHard problem + follow-ups, whiteboard-style.12 min
- 06Interview Post-MortemReviewing recordings, closing gaps, and reducing anxiety.6 min