list - 如何在scala中按周将列表分成组

Question

case class Test(dayOfWeek:Int,b:Int=Random.nextInt)
val data=(3 to 100).map(_ % 7).map(Test(_))

如何将数据分组，每组有一周的数据，如果一周不完整，也有一组。所以这个组应该是

Group 1: (3,4,5,6)   // the number here is the dayOfWeek
Group 2: (0,1,2,3,4,5,6)
Group 3: (0,1,2,3,4,5,6)
...
last Group:(0,1,2)

Answer 1

Scala 的集合非常强大，这应该在几行中完成:

val (firstWeek, nextWeeks) = data.span(_.dayOfWeek != 0)
val weeks = (firstWeek :: nextWeeks.grouped(7).toList).dropWhile(_.isEmpty)

查看 span 的文档和 grouped here .

println(weeks.zipWithIndex.map {
  case (week, i) => s"Group $i: (${week.map(_.dayOfWeek).mkString(",")})"
}.mkString("\n"))

输出:

Group 0: (3,4,5,6)
Group 1: (0,1,2,3,4,5,6)
Group 2: (0,1,2,3,4,5,6)
[snip]
Group 12: (0,1,2,3,4,5,6)
Group 13: (0,1,2,3,4,5,6)
Group 14: (0,1,2)