Using ReduceByKey to group list of values

Question

I want to group list of values per key and was doing something like this:

sc.parallelize(Array((\"red\", \"zero\"), (\"yellow\", \"one\"), (\"red\", \"two\")         


        

Answer 1

sc.parallelize(Array(("red", "zero"), ("yellow", "one"), ("red", "two")))
.map(t => (t._1,List(t._2)))
.reduceByKey(_:::_)
.collect()

Array[(String, List[String])] = Array((red,List(zero, two)), (yellow,List(one)))