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//===----------------------------------------------------------------------===//
//
// This source file is part of the Swift Collections open source project
//
// Copyright (c) 2021 - 2024 Apple Inc. and the Swift project authors
// Licensed under Apache License v2.0 with Runtime Library Exception
//
// See https://swift.org/LICENSE.txt for license information
//
//===----------------------------------------------------------------------===//
#if !COLLECTIONS_SINGLE_MODULE
import InternalCollectionsUtilities
#endif
// `OrderedSet` does not directly conform to `SetAlgebra` because its definition
// of equality conflicts with `SetAlgebra` requirements. However, it still
// implements most `SetAlgebra` requirements (except `insert`, which is replaced
// by `append`).
//
// `OrderedSet` also provides an `unordered` view that explicitly conforms to
// `SetAlgebra`. That view implements `Equatable` by ignoring element order,
// so it can satisfy `SetAlgebra` requirements.
extension OrderedSet {
/// Returns a Boolean value that indicates whether this set is a subset of
/// the given set.
///
/// Set *A* is a subset of another set *B* if every member of *A* is also a
/// member of *B*, ignoring the order they appear in the two sets.
///
/// let a: OrderedSet = [1, 2, 3, 4]
/// let b: OrderedSet = [4, 2, 1]
/// b.isSubset(of: a) // true
///
/// - Parameter other: Another set.
///
/// - Returns: `true` if the set is a subset of `other`; otherwise, `false`.
///
/// - Complexity: Expected to be O(`self.count`) on average, if `Element`
/// implements high-quality hashing.
@inlinable
public func isSubset(of other: Self) -> Bool {
guard other.count >= self.count else { return false }
for item in self {
guard other.contains(item) else { return false }
}
return true
}
// Generalizations
/// Returns a Boolean value that indicates whether this set is a subset of
/// the given set.
///
/// Set *A* is a subset of another set *B* if every member of *A* is also a
/// member of *B*, ignoring the order they appear in the two sets.
///
/// let a: OrderedSet = [1, 2, 3, 4]
/// let b: OrderedSet = [4, 2, 1]
/// b.isSubset(of: a.unordered) // true
///
/// - Parameter other: Another set.
///
/// - Returns: `true` if the set is a subset of `other`; otherwise, `false`.
///
/// - Complexity: Expected to be O(`self.count`) on average, if `Element`
/// implements high-quality hashing.
@inlinable
@inline(__always)
public func isSubset(of other: UnorderedView) -> Bool {
isSubset(of: other._base)
}
/// Returns a Boolean value that indicates whether this set is a subset of
/// the given set.
///
/// Set *A* is a subset of another set *B* if every member of *A* is also a
/// member of *B*, ignoring the order they appear in the two sets.
///
/// let a: OrderedSet = [1, 2, 3, 4]
/// let b: Set = [4, 2, 1]
/// b.isSubset(of: a) // true
///
/// - Parameter other: Another set.
///
/// - Returns: `true` if the set is a subset of `other`; otherwise, `false`.
///
/// - Complexity: Expected to be O(`self.count`) on average, if `Element`
/// implements high-quality hashing.
@inlinable
public func isSubset(of other: Set<Element>) -> Bool {
guard other.count >= self.count else { return false }
for item in self {
guard other.contains(item) else { return false }
}
return true
}
/// Returns a Boolean value that indicates whether this set is a subset of
/// the elements in the given sequence.
///
/// Set *A* is a subset of another set *B* if every member of *A* is also a
/// member of *B*, ignoring the order they appear in the two sets.
///
/// let a: Array = [1, 2, 3, 4]
/// let b: OrderedSet = [4, 2, 1]
/// b.isSubset(of: a) // true
///
/// - Parameter other: A finite sequence.
///
/// - Returns: `true` if the set is a subset of `other`; otherwise, `false`.
///
/// - Complexity: Expected to be O(`self.count` + *n*) on average, where *n*
/// is the number of elements in `other`, if `Element` implements
/// high-quality hashing.
@inlinable
public func isSubset(
of other: some Sequence<Element>
) -> Bool {
guard !isEmpty else { return true }
if let other = _specialize(other, for: Self.self) {
return isSubset(of: other)
}
var it = self.makeIterator()
let first = it.next()!
if let match = other._customContainsEquatableElement(first) {
// Fast path: the sequence has fast containment checks.
guard match else { return false }
while let item = it.next() {
guard other.contains(item) else { return false }
}
return true
}
return _UnsafeBitSet.withTemporaryBitSet(capacity: count) { seen in
// Mark elements in `self` that we've seen in `other`.
var c = 0
for item in other {
if let index = _find(item).index {
if seen.insert(index) {
c &+= 1
if c == self.count {
// We've seen enough.
return true
}
}
}
}
return false
}
}
}
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