交作业
func getSubsetsOfSet2<T>(set: Set<T>) -> Array<Set<T>> {
    let elements = Array(set)
    return getSubsetsOfSet4(elements: elements, index: elements.count-1)
}
func getSubsetsOfSet4<T>(elements: Array<T>, index: Int) -> Array<Set<T>> {
    var subSets = Array<Set<T>>() // 子集的数组
    // 先添加空集
    subSets.append(Set([]))
    // 以下获取每位元素加入的非空子集
    for element in elements{
        for subSet in subSets{
            var subSetWithCurrent = subSet
            subSetWithCurrent.insert(element)
            subSets.append(subSetWithCurrent)
        }
      print("当前元素为:\(element),【选】,子集为:\(subSets)")
    }
    print(">>>>>>>>>>所有子集为:\(subSets)")
    return subSets
}

let set0:Set<Int> = [1,2,3]
getSubsetsOfSet2(set: set0)