ztn-zotan-swift-algorithms/Guides

Guides

These guides describe the design and intention behind the APIs included in the Algorithms library. For further reading, see the announcement on swift.org and the official documentation.

Contents

Combinations / permutations

• combinations(ofCount:): Combinations of particular sizes of the elements in a collection.
• permutations(ofCount:): Permutations of a particular size of the elements in a collection, or of the full collection.
• uniquePermutations(ofCount:): Permutations of a collection's elements, skipping any duplicate permutations.

Mutating algorithms

• rotate(toStartAt:), rotate(subrange:toStartAt:): In-place rotation of elements.
• stablePartition(by:), stablePartition(subrange:by:): A partition that preserves the relative order of the resulting prefix and suffix.

Combining collections

• chain(_:_:): Concatenates two collections with the same element type.
• cycled(), cycled(times:): Repeats the elements of a collection forever or a set number of times.
• joined(by:): Concatenate sequences of sequences, using an element or sequence as a separator, or using a closure to generate each separator.
• product(_:_:): Iterates over all the pairs of two collections; equivalent to nested for-in loops.

Subsetting operations

• compacted(): Drops the nils from a sequence or collection, unwrapping the remaining elements.
• partitioned(by:): Returns the elements in a sequence or collection that do and do not match a given predicate.
• randomSample(count:), randomSample(count:using:): Randomly selects a specific number of elements from a collection.
• randomStableSample(count:), randomStableSample(count:using:): Randomly selects a specific number of elements from a collection, preserving their original relative order.
• striding(by:): Returns every nth element of a collection.
• suffix(while:): Returns the suffix of a collection where all element pass a given predicate.
• trimmingPrefix(while:), trimmingSuffix(while), trimming(while:): Returns a slice by trimming elements from a collection's start, end, or both. The mutating trim... methods trim a collection in place.
• uniqued(), uniqued(on:): The unique elements of a collection, preserving their order.
• minAndMax(), minAndMax(by:): Returns the smallest and largest elements of a sequence.

Partial sorting

• min(count:), max(count:), min(count:sortedBy:), max(count:sortedBy:): Returns the smallest or largest elements of a collection, sorted by a predicate.

Other useful operations

• adjacentPairs(): Lazily iterates over tuples of adjacent elements.
• chunked(by:), chunked(on:), chunks(ofCount:): Eager and lazy operations that break a collection into chunks based on either a binary predicate or when the result of a projection changes or chunks of a given count.
• firstNonNil(_:): Returns the first non-nil result from transforming a sequence's elements.
• grouped(by:): Group up elements using the given closure, returning a Dictionary of those groups, keyed by the results of the closure.
• indexed(): Iterate over tuples of a collection's indices and elements.
• interspersed(with:): Place a value between every two elements of a sequence.
• keyed(by:), keyed(by:resolvingConflictsBy:): Returns a Dictionary that associates elements of a sequence with the keys returned by the given closure.
• partitioningIndex(where:): Returns the starting index of the partition of a collection that matches a predicate.
• reductions(_:), reductions(_:_:): Returns all the intermediate states of reducing the elements of a sequence or collection.
• split(maxSplits:omittingEmptySubsequences:whereSeparator), split(separator:maxSplits:omittingEmptySubsequences): Lazy versions of the Standard Library's eager operations that split sequences and collections into subsequences separated by the specified separator element.
• windows(ofCount:): Breaks a collection into overlapping subsequences where elements are slices from the original collection.