Post History
Scala 3, 68 bytes _.zipWithIndex.flatMap(_.zipWithIndex.filter(_._1)map(_._2)map _.->) Try it in Scastie! Takes a List[List[Boolean]], returns a List[(Int, Int)]. This abuses underscores a ...
Answer
#2: Post edited
by
user
·
2021-04-19T18:42:47Z (about 3 years ago)
- # Scala 3, 68 bytes
- ```scala
- _.zipWithIndex.flatMap(_.zipWithIndex.filter(_._1)map(_._2)map _.->)
- ```
- [Try it in Scastie!](https://scastie.scala-lang.org/RDjAuL1cTmqhAmtlwpIJRQ)
Takes a `List[List[Boolean]]`, returns a `List[(Int, Int)]`.- Explanation:
- ```scala
- _.zipWithIndex //Zip each row with its index
- .flatMap( //Map every (row, index) tuple to a list of truthy indices,
- //then flatten
- _.zipWithIndex //Zip each element with its column
- .filter(_._1) //Keep the tuples where the element (_1) is true
- map(_._2) //Keep the second part of the tuple (the column)
- map _.->) //Make a 2-tuple with the row's index
- ```
- # Scala 3, 68 bytes
- ```scala
- _.zipWithIndex.flatMap(_.zipWithIndex.filter(_._1)map(_._2)map _.->)
- ```
- [Try it in Scastie!](https://scastie.scala-lang.org/RDjAuL1cTmqhAmtlwpIJRQ)
- Takes a `List[List[Boolean]]`, returns a `List[(Int, Int)]`. This abuses underscores a bit (which is why Scala 3 is needed), but I'm proud of it.
- Explanation:
- ```scala
- _.zipWithIndex //Zip each row with its index
- .flatMap( //Map every (row, index) tuple to a list of truthy indices,
- //then flatten
- _.zipWithIndex //Zip each element with its column
- .filter(_._1) //Keep the tuples where the element (_1) is true
- map(_._2) //Keep the second part of the tuple (the column)
- map _.->) //Make a 2-tuple with the row's index
- ```
#1: Initial revision
by
user
·
2021-04-19T18:42:16Z (about 3 years ago)
# Scala 3, 68 bytes
```scala
_.zipWithIndex.flatMap(_.zipWithIndex.filter(_._1)map(_._2)map _.->)
```
[Try it in Scastie!](https://scastie.scala-lang.org/RDjAuL1cTmqhAmtlwpIJRQ)
Takes a `List[List[Boolean]]`, returns a `List[(Int, Int)]`.
Explanation:
```scala
_.zipWithIndex //Zip each row with its index
.flatMap( //Map every (row, index) tuple to a list of truthy indices,
//then flatten
_.zipWithIndex //Zip each element with its column
.filter(_._1) //Keep the tuples where the element (_1) is true
map(_._2) //Keep the second part of the tuple (the column)
map _.->) //Make a 2-tuple with the row's index
```