从多维数组中删除重复项

However in Swift 4.1 (available with Xcode 9.3), Array<Element> now conforms to Equatable when its Element conforms to Equatable. This change is given in the changelog: SE-0143 现在，标准库类型Optional，Array，ArraySlice，ContiguousArray和Dictionary的元素类型符合Equatable时，它们符合Equatable协议.这允许==运算符进行组合(例如，可以将[Int : [Int?]?]类型的两个值与==进行比较)，以及使用为Equatable元素类型定义的各种算法，例如index(of:). SE-0143 The standard library types Optional, Array, ArraySlice, ContiguousArray, and Dictionary now conform to the Equatable protocol when their element types conform to Equatable. This allows the == operator to compose (e.g., one can compare two values of type [Int : [Int?]?] with ==), as well as use various algorithms defined for Equatable element types, such as index(of:).您的带有multiDimArr.removeDups()的示例将按照4.1中的预期进行编译和运行，并产生结果[[1, 2, 3], [1, 2, 4]].Your example with multiDimArr.removeDups() compiles and runs as expected in 4.1, yielding the result [[1, 2, 3], [1, 2, 4]].在Swift 4.0.3中，您可以通过为嵌套数组添加removeDups()的另一个重载来对其进行破解:In Swift 4.0.3, you could hack it by adding another overload of removeDups() for nested arrays:extension Array { func removeDups<T : Equatable>() -> [Element] where Element == [T] { var result = [Element]() for element in self{ if !result.contains(where: { element == $0 }) { result.append(element) } } return result }}let multiDimArr = [[1, 2, 3], [1, 2, 3], [1, 2, 4]]print(multiDimArr.removeDups()) // [[1, 2, 3], [1, 2, 4]]不幸的是，这确实导致了一些代码重复，但是至少在更新到4.1时您将能够摆脱它.This does unfortunately lead to some code duplication, but at least you'll be able to get rid of it when updating to 4.1.此示例无法在4.0.3或4.1中编译的事实:The fact that this example doesn't compile in either 4.0.3 or 4.1:if [1, 2] == [1, 2] { // error: Ambiguous use of operator '==' print("true")}是由于错误 SR-5944 引起的–编译器正在考虑将其用于由于IndexSet和IndexPath(两者均为ExpressibleByArrayLiteral)的==重载而导致模棱两可.但是，Swift应该将数组文字默认设置为Array，以解决歧义.is due to the bug SR-5944 – the compiler is considering it to be ambiguous due to == overloads for IndexSet and IndexPath (both of which are ExpressibleByArrayLiteral). But Swift should default an array literal to Array though, resolving the ambiguity.说:if [1, 2] as [Int] == [1, 2] { print("true")}或不导入Foundation即可解决问题.or not importing Foundation resolves the issue.最后，值得注意的是，如果Element类型也为Hashable，则removeDups()的性能可以得到改善，从而使其可以线性运行，而不是二次运行:Finally, it's worth noting that the performance of removeDups() can be improved if the Element type is also Hashable, allowing it to run in linear, rather than quadratic time:extension Array where Element : Hashable { func removeDups() -> [Element] { var uniquedElements = Set<Element>() return filter { uniquedElements.insert($0).inserted } }}在这里，我们正在使用一个集合来存储我们已经看到的元素，而忽略了我们已经插入到其中的任何元素.这也使我们可以将filter(_:)，用作@Alexander点.Here we're using a set to store the elements that we've seen, omitting any that we've already inserted into it. This also allows us to use filter(_:), as @Alexander points out.并且在Swift 4.2中，当Element为Hashable时，也有条件地符合Hashable:And in Swift 4.2, Array also conditionally conforms to Hashable when its Element is Hashable: SE-0143 现在，标准库类型Optional，Array，ArraySlice，ContiguousArray，Dictionary，DictionaryLiteral，Range和ClosedRange的元素或绑定类型符合Hashable协议(视情况而定)符合Hashable.这使得合成的Hashable实现可用于包含这些类型的存储属性的类型. SE-0143 The standard library types Optional, Array, ArraySlice, ContiguousArray, Dictionary, DictionaryLiteral, Range, and ClosedRange now conform to the Hashable protocol when their element or bound types (as the case may be) conform to Hashable. This makes synthesized Hashable implementations available for types that include stored properties of these types. 这篇关于从多维数组中删除重复项的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持！ 上岸，阿里云！