Scala By Example: Case 类与模式匹配 习题

1: abstract class IntTree

2: case object EmptyTree extends IntTree

3: case class Node(elem: Int, left: IntTree, right: IntTree) extends IntTree

4:

5: def contains(t: IntTree, v: Int): Boolean = t match {

6:     case EmptyTree => false

7:     case Node(e, l, r) => e == v || contains(l, v) || contains(r, v)

8: }

9:

10: def insert(t: IntTree, v: Int): IntTree = t match {

11:     case EmptyTree => Node(v, EmptyTree, EmptyTree)

12:     case Node(e, l, r) =>

13:         if(e == v) t

14:         else if(e > v) Node(e, insert(l, v), r)

15:         else Node(e, l, insert(r, v))

16: }