package tree object MaximumByFold { def maximum(t: Tree[Int]): Int = Fold.fold(t)(a => a)(_ max _) 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(maximum(tree)) } }
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原文：http://www.cnblogs.com/JonkeyGuan/p/5424833.html