快速检查一个数组是否包含另一个数组的元素

Question

我需要检查一个数组是否至少包含另一个数组的一个或多个元素，并快速将它们打印出来。这是我的情况：

var array1 = ["user1", "user2", "user3", "user4"]
var array2 = ["user3, "user5", "user7", "user9, "user4"]

//I need to get back an array that says that both the arrays contains ex. "user3" and "user4"

我搜索了网络，但我只找到了相反的答案，可以帮助检查两个数组之间是否存在差异array.symmetricDifference()

有什么帮助吗？？？谢谢

Answer 1

You can simply create a set from your first collection and get its intersection with the other collection:

let array1 = ["user1", "user2", "user3", "user4"]
let array2 = ["user3", "user5", "user7", "user9", "user4"]
let intersection = Array(Set(array1).intersection(array2)) // ["user4", "user3"] 

请注意，结果集合的顺序是不可预测的。如果您想保留第一个集合的顺序，您可以创建第二个集合的集合并过滤无法插入其中的元素：

var set = Set(array2)
let intersection = array1.filter { !set.insert($0).inserted }  // ["user3", "user4"]

您还可以在 RangeReplaceableCollection 上创建自己的交集方法：

extension RangeReplaceableCollection {
    func intersection<S: Sequence>(_ sequence: S) -> Self where S.Element == Element, Element: Hashable {
        var set = Set(sequence)
        return filter { !set.insert($0).inserted }
    }
}

用法：

let intersection = array1.intersection(array2)  // ["user3", "user4"]