Counta.swift

enum AttendanceType: Int {
	case paid, free, reset


}

extension Collection where Element == AttendanceType {

	var itemSort: [Int] {

		var output = [Int]()
		var current = 0

		self.reversed().forEach { item in
			switch item {
			case .free:
				output.append(0)
			case .paid:
				current += 1
				output.append(current)
			case .reset:
				current = 0
				output.append(current)
			}
		}
		return output.reversed()
	}
}

let basic8: [AttendanceType] = [.free, .free, .reset]
let basic8a = basic8.itemSort
assert(basic8a == [0,0,0])

let basic1: [AttendanceType] = [.paid, .paid, .paid]
let basic1a = basic1.itemSort
assert(basic1a == [3,2,1])

let basic2: [AttendanceType] = [.paid, .free, .paid, .paid, .paid]
let basic2a = basic2.itemSort
assert(basic2a == [4, 0, 3, 2, 1])

let basic3: [AttendanceType] = [.reset, .paid, .free, .paid, .reset, .paid, .paid]
let basic3a = basic3.itemSort
assert(basic3a == [0, 2, 0, 1, 0, 2, 1])

let basic4: [AttendanceType] = [.free, .paid, .free, .reset, .paid, .paid, .paid, .paid]
let basic4a = basic4.itemSort
assert(basic4a == [0, 1, 0, 0, 4, 3, 2, 1])

let basic5: [AttendanceType] = [.free, .paid, .free, .reset, .paid, .paid, .paid, .paid]
let basic5a = basic5.itemSort
assert(basic5a == [0, 1, 0, 0, 4, 3, 2, 1])

let basic6: [AttendanceType] = [.paid, .paid, .reset, .paid, .free, .paid, .reset, .paid, .paid, .paid]
let basic6a = basic6.itemSort
assert(basic6a == [2, 1, 0, 2, 0, 1, 0, 3, 2, 1])