Swift coding questions

Find the two numbers in an array that add up to a target, in one pass.

Check that every bracket in a string is closed by the same type, in the right order.

Find the biggest profit from one buy and one later sell, in a single pass.

Use binary search to find the first broken CI build with as few checks as possible.

Reverse a singly linked list in place by turning every next pointer around.

Merge overlapping calendar events into busy blocks by sorting first, then scanning once.

Group words made of the same letters by using a dictionary with a smart key.

Count how often each hashtag is used and return the k most popular ones.

For each index, multiply every other number, without division, using prefix and suffix products.

Find the longest run of unique characters with a sliding window and a dictionary.

Find the closest view that contains two given views, using superview pointers.

Walk a view tree level by level with breadth-first search and return the names of each level.

Build a prefix tree that returns sorted search suggestions without scanning every word.

Count connected regions of filled pixels in a mask with flood fill (the "number of islands" problem).

Rotate an n x n pixel grid 90 degrees clockwise in place, with a transpose and a mirror.

Build a generic binary heap with push, pop and peek in O(log n), ordered by any comparator.

Find a build order for Swift modules from their dependencies with a topological sort, and detect cycles.

Build a generic cache that drops the least recently used item when it is full. Every operation must be O(1).

Run an action only after the calls stop for a short time, like a search box that waits until the user stops typing.

Run an action at most once per time window. The first call runs right away, and the last call in the window runs when the window ends.

Retry a failing async operation, and double the wait time after each failure.

Transform an array with async work in parallel, keep the input order, and never run more than N tasks at once.

Build a bank account as an actor so many tasks can deposit, withdraw and transfer at the same time without data races.

Decode a real-looking API response with snake_case keys, ISO 8601 dates, nested and optional fields, and an enum that survives new values.

Write a @Clamped property wrapper that keeps a value inside a range, like a volume from 0 to 100.

Build a typed publish/subscribe bus where a subscription ends by itself when its token is released.

Parse custom-scheme deep links and universal links into a type-safe Route enum with URLComponents.

Parse version strings like "2.0.0-beta.1" and sort them correctly with Comparable, following the semver rules.

Turn a date into "just now", "5m ago", "2h ago", "yesterday", "3d ago" or a short date, with the current time injected for testing.

Build a small DI container that registers factories by type, supports singleton and transient scopes, and throws for missing types.

Write a generic memoize function that caches results, plus a version that also works for recursive functions like Fibonacci.

Build an NSCache-like cache with a total cost limit that evicts the least recently used items until it fits.

Build an actor that loads pages for an infinite list, ignores duplicate loads while one is running, and stops at the last page.