package tree object Fold { def fold[A, B](t: Tree[A])(f: A => B)(g: (B, B) => B): B = t match { case Leaf(a) => f(a) case Branch(l, r) => g(fold(l)(f)(g), fold(r)(f)(g)) } def main(args: Array[String]): Unit = { val tree = Branch(Leaf(1), Branch(Branch(Branch(Leaf(3), Branch(Leaf(5), Leaf(6))), Leaf(4)), Leaf(2))) println(fold(tree)(_ => 1)(_ + _ + 1)) } }
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时间: 2024-11-10 15:41:22