在Scala中合并两个列表 [英] Combining two lists in Scala

问题描述

从2个形式为List[(Int, String)的列表中:

From 2 lists of the form List[(Int, String):

l1 = List((1,"a"),(3,"b"))
l2 = List((3,"a"),(4,"c"))

我如何结合Integer，其中String相同，以获得第三个列表:

how can I combine the Integers where the Strings are the same to get this third list:

l3 = List((4,"a"),(3,"b"),(4,"c"))

现在，我遍历两个列表，并在字符串相同的情况下进行添加，但是我认为应该有一个简单的模式匹配解决方案.

Right now I'm traversing both of the lists and adding if the strings are the same, but I think there should be a simple solution with pattern matching.

推荐答案

val l = l1 ::: l2
val m = Map[String, Int]()
(m /: l) {
  case (map, (i, s)) => { map.updated(s, i + (map.get(s) getOrElse 0))}
}.toList // Note: Tuples are reversed.

但是我想有一种更优雅的方式来制作updated部分.

But I suppose there is a more elegant way to do the updated part.

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