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scalaadjacency-listadjacency-matrix

How to convert Text file data into Adjucency list

I have following Graph Text file, It is big file I want to convert into adjacency List in scala. First few lines of the text file given below:

src, dst,dist  
A,C,5.0
A,B,8.0
B,C,6.0
B,D,7.0
B,A,8.0
C,A,5.0
C,B,6.0
D,B,7.0
D,E,8.0
E,D,8.0

I want to convert it into following format of adjucency list.

"A"->List((8.0,"B"),(5.0,"C"))

Please guide me what is good way convert it into adjacency list in scala.

Solution

  • Since there's been no followup:

     val zs = """A,C,5.0
A,B,8.0
B,C,6.0
B,D,7.0
B,A,8.0
C,A,5.0
C,B,6.0
D,B,7.0
D,E,8.0
E,D,8.0"""

    Parse the string into a Seq of Seq... 

    val as = zs.split('\n').toSeq.map(_.split(',').toSeq)

    Make it into key, value. Value is a a single-element Seq because it makes reduceByKey easy to use

    val bs = as.map{case Seq(k,v,d) => (k, Seq((v,d)))}.reduceByKey(_ ++ _)
// Map(E -> List((D,8.0)),
//     A -> List((C,5.0), (B,8.0)),
//     B -> List((C,6.0), (D,7.0), (A ,8.0)),
//     C -> List((A,5.0), (B,6.0)),
//     D -> List((B,7.0), (E,8.0)))

    Where a (slightly simplistic) reduceByKey is

    implicit class SparkOps[K, V]( xs:Traversable[(K,V)]) {
   def reduceByKey(f:(V,V)=>V)= 
       xs.groupBy(_._1).mapValues{x=>x.unzip._2.reduce(f)}

   }

    ("simplistic" because it always returns a Map rather than the same Traversable as the input).