A.val b = 2 * a // b 等于 Array(2,4,6) B.val b = a.map(_*2) // b 等于 Array(2,4,6) C.val b = for(elem <- a) yield 2 * elem // b 等于 Array(2,4,6) D.val b = for(elem <- a if elem % 2 == 0) yield 2 * elem // b 等于 Array(4)
A.15 B.120 C.200 D.300
A.def countdown(n:Int){ 0 to n foreach print } B.def countdown(n:Int){ (0 until n).reverse foreach print } C.def countdown(n:Int){ (0 to n).reverse foreach print } D.def countdown(n:Int){ (0 to n-1).reverse foreach print }