Blog

BFS finds shortest paths when every edge costs the same. Dijkstra's algorithm generalizes that to weighted graphs by always expanding the closest unvisited node next — the algorithm behind every routing map you've used.

Calendar conflicts, meeting rooms, and 'maximum non-overlapping tasks' are all interval problems that collapse into a single sort-then-scan pattern once you pick the right key to sort by.

A probabilistic data structure that answers set-membership queries in constant space by allowing false positives but never false negatives — and why Chrome, Cassandra, and CDNs all rely on that trade.

When an array changes and you still need fast range sum, min, or max queries, prefix sums stop working. Segment trees answer both range queries and point updates in logarithmic time.

One template solves permutations, subsets, N-Queens, and Sudoku. Learn the choose–explore–unchoose pattern and how pruning turns exponential search into something usable.

What Big-O actually measures, how to read a function's complexity straight from its shape, and why O(n log n) beats O(n²) long before n gets big.

LIFO and FIFO look trivial until you notice they power your call stack, undo history, browser navigation, and every BFS. Plus the classic interview patterns for each.

Build systems, package managers, and course schedulers all answer the same question: what order satisfies every dependency? Kahn's algorithm answers it — and detects impossible cycles.

The disjoint set union structure answers 'are these two connected?' in near-O(1) — with two optimizations you can write in twenty lines. Includes Kruskal's MST and cycle detection.

The operators every developer half-remembers — AND, OR, XOR, shifts — and the handful of tricks that turn them into fast, elegant solutions.