これ #CodePiece

CodePiece.swift

struct Reader: Sequence {
    struct Iterator: IteratorProtocol {
        func next() -> String? {
            readLine() 
        }
    }
    
    func makeIterator() -> Iterator {
        .init()
    }
}

Reader()
    .flatMap { $0.split(separator: " ") }
    .map { $0.lowercased() }
    .reduce(into: [String: Int]()) { d, w in d[w, default: 0] += 1 }
    .sorted { $0.1 > $1.1 }
    .forEach { print($0.key, $0.value) }