Question

我的两个清单如下：

val a = List((1430299869,"A",4200), (1430299869,"A",0))

val b = List((1430302366,"B",4100), (1430302366,"B",4200), (1430302366,"B",5000), (1430302366,"B",27017), (1430302366,"B",80), (1430302366,"B",9300), (1430302366,"B",9200), (1430302366,"A",5000), (1430302366,"A",4200), (1430302366,"A",80), (1430302366,"A",443), (1430302366,"C",4100), (1430302366,"C",4200), (1430302366,"C",27017), (1430302366,"C",5000), (1430302366,"C",80))

当我使用zip两个列表时如下：

val c = a zip b

它将结果返回为

List(((1430299869,A,4200),(1430302366,B,4100)), ((1430299869,A,0),(1430302366,B,4200)))

不是所有元组列表，我如何压缩以上所有数据？

编辑

预期结果为两个列表的组合，如：

List((1430299869,"A",4200), (1430299869,"A",0),(1430302366,"B",4100), (1430302366,"B",4200), (1430302366,"B",5000), (1430302366,"B",27017), (1430302366,"B",80), (1430302366,"B",9300), (1430302366,"B",9200), (1430302366,"A",5000), (1430302366,"A",4200), (1430302366,"A",80), (1430302366,"A",443), (1430302366,"C",4100), (1430302366,"C",4200), (1430302366,"C",27017), (1430302366,"C",5000), (1430302366,"C",80))

第二次修改

我试过了：

val d = for(((a,b,c),(d,e,f)) <- (a zip b)if(b.equals(e) && c.equals(f))) yield (d,e,f)

但由于(a zip b)而导致结果为空，但我将a zip b替换为a ++ b，然后显示以下错误：

构造函数无法实例化为期望的类型;

那么如何才能获得匹配的元组呢？

Answer 1

只需将一个列表添加到另一个列表：

a ++ b

Answer 2

在压缩（配对）列表中的所有数据时，首先考虑一个简短的输入来说明案例，

val a = (1 to 2).toList
val b = (10 to 12).toList

然后，例如，理解可以传达需求，

for (i <- a; j <- b) yield (i,j)

提供

List((1,10), (1,11), (1,12), 
     (2,10), (2,11), (2,12))

<强>更新

从OP最新更新，考虑专用过滤功能，

type triplet = (Int,String,Int)

def filtering(key: triplet, xs: List[triplet]) = 
  xs.filter( v => key._2 == v._2 && key._3 == v._3 )

然后将其应用于flatMap，

a.flatMap(filtering(_, b))
List((1430302366,A,4200))

另外一个步骤是将其封装在隐式类

中

implicit class OpsFilter(val keys: List[triplet]) extends AnyVal {
  def filtering(xs: List[triplet]) = {
    keys.flatMap ( key => xs.filter( v => key._2 == v._2 && key._3 == v._3 ))
  }
}

同样，

a.filtering(b)
List((1430302366,A,4200))

Answer 3

a zip b创建a和b中的元素对列表。

您最有可能寻找的是列表连接，即a ++ b

Scala列表中不同大小的元组拉链问题？

3 个答案: