scala code

scala

对map的value做group操作

  val map = Map("w1" -> Set("w1"),
    "w2" -> Set("w2", "b4"),
    "w3" -> Set("w3", "b5"),
    "b4" -> Set("b4", "w2"),
    "b5" -> Set("b5", "w3"))
  val list = map.toList
  println(list)
  def mapGroup[K, V, L[_]](list: List[(K, L[V])]): List[L[V]] = list match {
    case List() => Nil
    case head :: rest =>
      head._2 :: mapGroup(rest.filter{ case (k, v) =>
        v != head._2
      })
  }
  println(mapGroup(list))

哈哈，逗比了吧！更简洁的方法：

def mapGroup2[K, V, L[_]](map: Map[K, L[V]]): List[L[V]] = map.values.toList.distinct
println(mapGroup2(map))

哈哈，又是我; 但是，第一个方法稍微改造一下可以保留group之后的keys

def mapGroup3[K, V, L[_]](list: List[(K, L[V])]): (List[List[K]], List[L[V]]) = list match {
    case List() => (Nil, Nil)
    case head :: rest =>
      val (ks, vs) = mapGroup3(rest.filter{ case (k, v) =>
        v != head._2
      })
      ((head._1 :: rest.filter{ case (k, v) =>
        v == head._2
      }.map(_._1)) :: ks,
      head._2 :: vs)
  }

result

List((w2,Set(w2, b4)), (b4,Set(b4, w2)), (w1,Set(w1)), (b5,Set(b5, w3)), (w3,Set(w3, b5)))
List(Set(w2, b4), Set(w1), Set(b5, w3))
List(Set(w2, b4), Set(w1), Set(b5, w3))
(List(List(w2, b4), List(w1), List(b5, w3)),List(Set(w2, b4), Set(w1), Set(b5, w3)))

自旋锁

class SpinLock {
    import java.util.concurrent.atomic.AtomicReference
    private val sign : AtomicReference[Thread] = new AtomicReference
    def lock {
      val current = Thread.currentThread
      while(!sign.compareAndSet(null, current)){
      }
    }
    def unlock {
      val current = Thread.currentThread
      sign.compareAndSet(current, null)
    }
  }
  //使用
    spinLock.lock
    try {
      //...
    } finally {
      spinLock.unlock
    }