Everything, in order

The row of numbered boxes that everything else is built on.

The grid is a fiction. Memory is one flat line — and that's why row-major is fast.

A hash map that threw away the values — and answers 'seen this before?' instantly.

Throw away half the list with every single question.

Compare neighbours, swap if they're wrong. Repeat until calm.

How you actually sort a hand of cards, without being taught.

Pick a pivot, split around it, and let the halves sort themselves.

Insertion sort, but values are allowed to leap instead of crawl.

Sort by the last digit first. It sounds backwards, and it's the only way it works.

First in, first out. Fairness, as a data structure.

A queue in a fixed array that never shuffles — the pointers go round instead.

One extra pointer per node — and the singly linked list's worst flaw disappears.

A tree that keeps one promise — smaller left, bigger right — so it can search fast.

A tree that always keeps the biggest thing on top, ready to grab.

Every node stores the answer for a whole range — so a range query stops early.

Explore a network in rings, nearest first — using a queue.

Put jobs in an order where nothing happens before what it depends on.

Slower than Dijkstra, and it can do the one thing Dijkstra can't.

Merge groups and ask 'are these two connected?' — in effectively constant time.

Two markers moving toward each other turn an O(n²) search into O(n).

A stack kept in order — so one new value can answer many old questions at once.

Guess, explore, and when it dead-ends — put it back exactly as it was.