地圖一個值的所有值與一個共同的關係斯卡拉

Question

有一組數據：

{sentenceA1}{\t}{sentenceB1} 
{sentenceA1}{\t}{sentenceB2} 
{sentenceA2}{\t}{sentenceB1} 
{sentenceA3}{\t}{sentenceB1} 
{sentenceA4}{\t}{sentenceB2}  

我想一個sentenceA映射到所有具有共同sentenceB Scala中這樣的結果將是什麼句子像這樣：

{sentenceA1}->{sentenceA2,sentenceA3,sentenceA4} or 

{sentenceA2}->{sentenceA1, sentenceA3} 

Answer 1

val lines = List(
    "sentenceA1\tsentenceB1", 
    "sentenceA1\tsentenceB2", 
    "sentenceA2\tsentenceB1", 
    "sentenceA3\tsentenceB1", 
    "sentenceA4\tsentenceB2" 
) 

val afterSplit = lines.map(_.split("\t")) 

val ba = afterSplit 
    .groupBy(_(1)) 
    .mapValues(_.map(_(0))) 

val ab = afterSplit 
    .groupBy(_(0)) 
    .mapValues(_.map(_(1))) 

val result = ab.map { case (a, b) => 
    a -> b.foldLeft(Set[String]())(_ ++ ba(_)).diff(Set(a)) 
}