Create a list of lists from two columns in a data frame - Scala - arrays

Question

I have a data frame where passengerId and path are Strings. The path represents the flight path of the passenger so passenger 10096 started in country CO and traveled to country BM. I need to find out the longest amount of flights each passenger has without traveling to the UK.
+-----------+--------------------+
|passengerId| path|
+-----------+--------------------+
| 10096| co,bm|
| 10351| pk,uk|
| 10436| co,co,cn,tj,us,ir|
| 1090| dk,tj,jo,jo,ch,cn|
| 11078| pk,no,fr,no|
| 11332|sg,cn,co,bm,sg,jo...|
| 11563|us,sg,th,cn,il,uk...|
| 1159| ca,cl,il,sg,il|
| 11722| dk,dk,pk,sg,cn|
| 11888|au,se,ca,tj,th,be...|
| 12394| dk,nl,th|
| 12529| no,be,au|
| 12847| cn,cg|
| 13192| cn,tk,cg,uk,uk|
| 13282| co,us,iq,iq|
| 13442| cn,pk,jo,us,ch,cg|
| 13610| be,ar,tj,no,ch,no|
| 13772| be,at,iq|
| 13865| be,th,cn,il|
| 14157| sg,dk|
+-----------+--------------------+
I need to get it like this.
val data = List(
(1,List("UK","IR","AT","UK","CH","PK")),
(2,List("CG","IR")),
(3,List("CG","IR","SG","BE","UK")),
(4,List("CG","IR","NO","UK","SG","UK","IR","TJ","AT")),
(5,List("CG","IR"))
I'm trying to use this solution but I can't make this list of lists. It also seems like the input used in the solution has each country code as a separate item in the list, while my path column has the country codes listed as a single element to describe the flight path.

Answer 1

If the goal is just to generate the list of destinations from a string, you can simply use split:
df.withColumn("path", split('path, ","))
If the goal is to compute the maximum number of steps without going to the UK, you could do something like this:
df
// split the string on 'uk' and generate one row per sub journey
.withColumn("path", explode(split('path, ",?uk,?")))
// compute the size of each sub journey
.withColumn("path_size", size(split('path, ",")))
// retrieve the longest one
.groupBy("passengerId")
.agg(max('path_size) as "max_path_size")