Blog

Three linked list problems, one underlying playbook: dummy heads, divide-and-conquer merging, and the find-middle/reverse/interleave pipeline that makes LC 143 tractable.

One BFS template, three interview problems. Level-order, zigzag traversal, and right side view all reduce to the same queue loop with a small variation each time.

Post-order DFS, the global-state side-effect trick, and nested tree matching — four problems that teach you everything about recursive tree traversal in JavaScript.

The three-pointer pattern is the foundation of every linked list reversal. Understand it once and LC 206, 92, and 25 become variations on the same idea.

Two matrix search problems, two completely different optimal approaches. Learn when to use virtual 1D binary search vs the staircase elimination — the distinction that trips up most candidates.

A rotated sorted array still has structure you can exploit. Learn the one insight that makes O(log n) search possible — and how to handle duplicates.

Binary search isn't just for sorted arrays. Learn to search the range of possible answers to crack Koko Eating Bananas, Ship Packages, and a whole category of hard problems.

Two pointers, one pass, O(n) — learn how the variable-size sliding window grows and shrinks to solve substring and subarray problems efficiently.

Stop re-summing from scratch — the fixed-size sliding window reduces O(n·k) nested loops to a single O(n) pass by adding one element and dropping one.