无水scala入群题 —— https://bitbucket.org/snippets/centaur/98qey

FlowLayout.scala

case class Size(width: Double, height: Double)

case class Point(x: Double, y: Double)

case class Row(origin: Point, children: List[Size], hSpacing: Double) {
  lazy val widthWithSpacing = children.map(_.width + hSpacing).sum
  lazy val maxHeight = children.map(_.height).max
  lazy val getRectOrigins: Seq[Point] = {
    children.foldRight(List[Point](origin)) { (curr, points) =>
      points match {
        case last :: rest =>
          Point(last.x + curr.width + hSpacing, origin.y) ::
            Point(last.x, origin.y + (maxHeight / 2) - (curr.height / 2)) :: rest
      }
    }.tail.reverse
  }
}

object FlowLayout {
  def layout(parentWidth: Double, padding: Double, vSpacing: Double, hSpacing: Double, children: Seq[Size]): Seq[Point] = {
    children.foldLeft(List[Row]()) {(rows, curr) => rows match {
        case Nil => Row(Point(padding, padding), List(curr), hSpacing) :: Nil
        case row :: rest =>
          if(row.widthWithSpacing + curr.width + 2 * padding <= parentWidth) {
            Row(row.origin, curr :: row.children, hSpacing) :: rest
          } else {
            Row(Point(padding, row.origin.y + vSpacing + row.maxHeight), curr :: Nil, hSpacing) :: rows
          }
      }
    }.reverse.flatMap(_.getRectOrigins)
  }
}

Problem.md

在一个以左上角为原点（0.0, 0.0）的二维坐标系（这也是计算机显示设备常用的坐标系）中， 已知一个宽度（parentWidth）固定的矩形区域parent，指定它的内边距（padding，四个方向相同）， 将一组子矩形在其中进行流式布局（Flow Layout）：每一行从左至右排列，第一个子矩形左上角与parent左上角的水平距离为padding， 相邻子矩形之间的水平间距为hSpacing，如果加入下一个子矩形会导致宽度超出parentWidth，则此子矩形成为下一行的第一项 。每一行的高度由其中最高的子矩形确定，其它子矩形垂直居中。行与行之间的垂直间距为vSpacing。如图：

图解

每一个矩形的宽高由 case class Size(width: Double, height: Double) 表示，点坐标由 case class Point(x: Double, y: Double) 表示。 请编写方法 def layout(parentWidth: Double, padding: Double, vSpacing: Double, hSpacing: Double, children: Seq[Size]): Seq[Point] 返回经过布局后所有子矩形的左上角坐标（以parent左上角为原点），需要保留次序。 可以美好假设每一个子矩形的宽度小于parentWidth - 2*padding，因此一定有解。

Test.scala

import org.scalatest._
import layout._
import layout.FlowLayout._

class Test extends FlatSpec with Matchers {
  "Original test" should "be passed" in {
    assert(layout(parentWidth = 10.0, padding = 0, vSpacing = 0, hSpacing = 0, Seq(Size(5, 7), Size(5, 5))) == Seq(Point(0.0, 0.0), Point(5.0, 1.0)))
    assert(layout(parentWidth = 10.0, padding = 0, vSpacing = 3.0, hSpacing = 0, Seq(Size(5, 7), Size(5, 5))) == Seq(Point(0.0, 0.0), Point(5.0, 1.0)))
    assert(layout(parentWidth = 10.0, padding = 0.0, vSpacing = 0, hSpacing = 1.0, Seq(Size(5, 7), Size(5, 5))) == Seq(Point(0.0, 0.0), Point(0.0, 7.0)))
    assert(layout(parentWidth = 10.0, padding = 1.0, vSpacing = 0, hSpacing = 0, Seq(Size(5, 7), Size(5, 5))) == Seq(Point(1.0, 1.0), Point(1.0, 8.0)))
    assert(layout(parentWidth = 10.0, padding = 1.0, vSpacing = 1.0, hSpacing = 0, Seq(Size(5, 7), Size(5, 5))) == Seq(Point(1.0, 1.0), Point(1.0, 9.0)))
    assert(layout(parentWidth = 10.0, padding = 1.0, vSpacing = 1.0, hSpacing = 1.0, Seq(Size(5, 7), Size(5, 5))) == Seq(Point(1.0, 1.0), Point(1.0, 9.0)))
    assert(layout(parentWidth = 10.0, padding = 1.0, vSpacing = 1.0, hSpacing = 0, Seq(Size(5, 7))) == Seq(Point(1.0, 1.0)))
    assert(layout(parentWidth = 10.0, padding = 1.0, vSpacing = 1.0, hSpacing = 1.0, Seq()) == Seq())
  }
}