Knowledge Hub
Topic-wise resources designed to help students learn deeply and connect concepts to interview skills.
Arrays
Start from fundamentals and progress through interview-heavy array patterns with focused, easy-to-follow resources.
Read nowAmortized analysis
Understand why some structures feel “always fast” even when an occasional step copies many elements — with student-friendly Python examples.
Read nowBinary search
Monotone search, lower bound, search on answer space, and interview patterns—step by step with Python.
Read nowTwo pointers
Pair indices moving along a line or on two sequences—basics, windows, merge walk, and interview patterns with Python.
Read nowStacks & queues
LIFO, FIFO, deques, and monotone structures—basics through LRU and monotonic patterns with Python.
Read nowTrie
Prefix tree for strings and bits—insert, search, and interview patterns with Python.
Read nowTree structures
BSTs, traversals, balanced trees, and structural tree questions with Python.
Read nowLinked lists
Node manipulation, cycles, middle-finding, and two-pointer patterns—Python first, with clear Node types.
Read nowBits & subset DP
Bitmasking, XOR tricks, subset enumeration, meet-in-the-middle, and SOS-style DP—with Python for students.
Read nowCombinatorics
Counting, permutations, inclusion–exclusion, and combinatorial generation—with Python you can run.
Read nowCoordinate tricks
Coordinate compression, areas, and ordering—bilingual lessons with Python (3 canonical skills).
Read nowDivide and conquer
Split problems in half, recurse, merge, and pick order statistics—student-friendly Python.
Read nowFoundations
Loops, I/O, and basic program structure—bilingual lessons with Python (41 canonical foundation skills).
Read nowGeneral & cross-cutting
Study habits and meta skills that help when a problem is messy or underspecified.
Read nowGreedy
Local choices, feasibility checks, and classic scheduling patterns—with Python.
Read nowHashing & frequency
Hash maps, sets, and count arrays—bilingual lessons with Python (23 canonical skills).
Read nowRecursion & backtracking
Exhaustive building and pruning of choices—bilingual lessons with Python (27 canonical skills).
Read nowSegment tree & range queries
Range updates/queries, lazy propagation, and similar structures—bilingual lessons with Python (38 canonical skills).
Read nowGraphs
Shortest paths, trees as graphs, connectivity, and flows—bilingual lessons with Python (81 canonical skills).
Read nowHeaps & priority queues
Binary heaps, `heapq`, and patterns for streaming top-k and scheduling.
Read nowNumber theory
Primes, divisibility, modular inverses, and CRT—bilingual lessons with Python (98 canonical skills).
Read nowMatrices
2D arrays, fast matrix power, linear recurrences, and transition matrices—in Python.
Read nowPrefix & difference
Prefix sums, running totals, difference arrays for range updates, and transformed arrays—explained with real-world examples and Python.
Read nowSliding window
Fixed and variable subarray/substring windows, two-pointer expansion and shrinking, validation maps, and minimum-window patterns—with Python and real-world hooks.
Read nowAlgorithms & complexity
Time/space tradeoffs, binary search on the answer, batching and offline queries, precomputation, and generic optimization patterns—bilingual lessons with Python (all canonical skills).
Read nowDynamic programming
State transitions, optimal substructure, and memoization—bilingual lessons with Python (29 canonical DP skills).
Read nowStrings
Characters, ASCII, indexing, filtering, replacement, validation, and more—bilingual lessons with Python (all 64 canonical string skills).
Read nowSorting
Comparison sorts, linear-time tricks, merges, inversions, and how ordering unlocks search and greedy ideas—explained in depth with real-world hooks.
Read now