scala的多種集合的使用(8)之隊列和棧的操作方法

1.使用隊列

隊列是一種那個先進先出的隊列。
1)創建一個隊列。

scala> import scala.collection.mutable.Queue
import scala.collection.mutable.Queue

scala> var fruits = Queue[String]()
fruits: scala.collection.mutable.Queue[String] = Queue()

scala> fruits += "apple"
res66: scala.collection.mutable.Queue[String] = Queue(apple)

scala> fruits += ("orange","banana")
res67: scala.collection.mutable.Queue[String] = Queue(apple, orange, banana)

scala> fruits ++= List("cherry","cocount")
res68: scala.collection.mutable.Queue[String] = Queue(apple, orange, banana, cherry, cocount)

scala> fruits.enqueue("pine")

scala> fruits
res70: scala.collection.mutable.Queue[String] = Queue(apple, orange, banana, cherry, cocount, pine)

2)dequeue每次從隊列頭部刪除一個元素。

scala> val next = fruits.dequeue
next: String = apple

scala> fruits
res72: scala.collection.mutable.Queue[String] = Queue(orange, banana, cherry, cocount, pine)

3)dequeueFirst和dequeueAll方法可以從隊列中刪除多個元素。

scala> var fruits = Queue[String]()
fruits: scala.collection.mutable.Queue[String] = Queue()

scala> fruits ++= List("cherry","cocount")
res76: scala.collection.mutable.Queue[String] = Queue(cherry, cocount)

scala> fruits ++= List("orange","apple")
res77: scala.collection.mutable.Queue[String] = Queue(cherry, cocount, orange, apple)

scala> fruits.dequeueFirst(_.startsWith("a"))
res79: Option[String] = Some(apple)

scala> fruits
res80: scala.collection.mutable.Queue[String] = Queue(cherry, cocount, orange)

scala> fruits.dequeueAll(_.length > 6)
res81: scala.collection.mutable.Seq[String] = ArrayBuffer(cocount)

scala> fruits
res82: scala.collection.mutable.Queue[String] = Queue(cherry, orange)

2.使用棧

棧是一種後進先出的數據結構。用push方法將元素入棧，用pop方法將元素出棧。
1)創建一個任意數據類型空的可變棧。

scala> import scala.collection.mutable.Stack
import scala.collection.mutable.Stack

scala> var ints = Stack[Int]()
ints: scala.collection.mutable.Stack[Int] = Stack()

2)在創建時給棧初始元素。

scala> val ints = Stack(1,2,3)
ints: scala.collection.mutable.Stack[Int] = Stack(1, 2, 3)

3)用push方法向棧中填充元素。

scala> var fruits = Stack[String]()
fruits: scala.collection.mutable.Stack[String] = Stack()

scala> fruits.push("apple")
res2: scala.collection.mutable.Stack[String] = Stack(apple)

scala> fruits.push("apple","orange","banana")
res3: scala.collection.mutable.Stack[String] = Stack(banana, orange, apple, appl

4)用pop方法將元素出棧。

scala> val next = fruits.pop
next: String = banana

scala> fruits
res4: scala.collection.mutable.Stack[String] = Stack(orange, apple, apple)

5)用top方法查看下一個元素。

scala> fruits.top
res5: String = orange

scala> fruits
res6: scala.collection.mutable.Stack[String] = Stack(orange, apple, apple)

6)用clear清空一個可變棧。

scala> fruits.clear

scala> fruits
res8: scala.collection.mutable.Stack[String] = Stack()