List of lists in Scala? [closed] - list

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I have a grid (that is declared as a List (of Lists)) and each 3*3 block for example is indexed as 0, the next 3*3 block is indexed as 1, etc.
I need to write a method that returns the elements (integers) in a particular block given an index.
For example : b(0) should give 1 0 0 4 1 2 7 0 0
1 0 0 | 4 0 2 | 5 0 7 |
4 1 2 | 0 0 3 | 6 8 0 |
7 0 0 | 0 0 9 | 0 0 1 |
----------------------
1 0 0 | 4 0 2 | 5 0 7 |
9 0 2 | 0 4 3 | 1 8 0 |
7 1 0 | 0 8 9 | 8 0 0 |
----------------------
1 0 0 | 4 0 2 | 5 0 7 |
4 0 2 | 0 1 9 | 6 2 0 |
7 0 0 | 0 0 9 | 0 0 1 |
----------------------

Answer 1

implicit class MatrixOps[T](val l: List[List[T]]) extends AnyVal {
def getBlock(index: Int, size: Int = 3): List[T] = {
l map (_ drop index * size) take size flatMap (_ take size)
}
}
override def main(args: Array[String]): Unit = {
val x = List(
List(1, 2, 3),
List(4, 5, 6)
)
println(x.getBlock(0))
println(x.getBlock(1))
}

Answer 2

Try with following function,
def block(i:Int, grid:List[List[Int]]) = grid.
grouped(3).
toList(i / 3).
map(_.grouped(3).toList(i % 3))
Here's that example with nice print method
def print(q:List[List[Int]]) = q.map(_.mkString("\t")).mkString("\n")
val grid = (1 to 81).toList.grouped(9).toList
scala> print(block(1))
res37: String =
4 5 6
13 14 15
22 23 24
(Sorry, Im too lazy to write a sudoku board as an example :) )
To get the list of integers, try flattern.
scala> block(1).flattern
res38: List[Int] = List(4, 5, 6, 13, 14, 15, 22, 23, 34)