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  1. object Main extends App {
  2. 	  val abc = (1 to 1000).toList
  3.  
  4.       val startTime1 = System.currentTimeMillis()
  5.       val v1 = abc.scanLeft(List[Int]()) {
  6.           (a, acc)=> a ++ List(acc)
  7.       }.tail
  8.       val endTime1 = System.currentTimeMillis()
  9.       println(s"1: ${endTime1 - startTime1} ms")
  10.  
  11.       val startTime2 = System.currentTimeMillis()
  12.       val v2 = (1 to abc.length).map(abc.take).toList
  13.       val endTime2 = System.currentTimeMillis()
  14.       println(s"2: ${endTime2 - startTime2} ms")
  15.  
  16.       val startTime3 = System.currentTimeMillis()
  17.       val v3 = abc.inits.toList.reverse.tail
  18.       val endTime3 = System.currentTimeMillis()
  19.       println(s"3: ${endTime3 - startTime3} ms")
  20.  
  21.       val startTime4 = System.currentTimeMillis()
  22.       val v4 = ((List.empty[List[Int]], List.empty[Int]) /: abc) { 
  23.           case ((all, cur), i) => val next = cur :+ i ; ((all :+ next, next)) 
  24.       }
  25.       val endTime4 = System.currentTimeMillis()
  26.       println(s"4: ${endTime4 - startTime4} ms")
  27.  
  28.       val startTime5 = System.currentTimeMillis()
  29.       val v5 = (List(List(abc.head)) /: abc.tail) {
  30.           case (all, i) => all :+ (all.last :+ i) 
  31.       }
  32.       val endTime5 = System.currentTimeMillis()
  33.       println(s"5: ${endTime5 - startTime5} ms")
  34. }
Success #stdin #stdout 1.44s 322240KB
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1: 130 ms
2: 165 ms
3: 373 ms
4: 187 ms
5: 172 ms
https://ideone.com/MtdFHf
language:
Scala (scala 2.12.8)
created:
9 years ago
visibility:
public

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