scala - 如何使用scala基于某些元素从元组列表中查找唯一元素？

Question

我有以下 list

val a = List(("name1","add1","city1",10),("name1","add1","city1",10),

("name2","add2","city2",10),("name2","add2","city2",20),("name3","add3","city3",20))

我想要基于元组的前三个值从上面的列表中获取不同的元素。从列表中查找不同元素时不应考虑第四个值。

我想要以下输出:

val output = List(("name1","add1","city1",10),("name2","add2","city2",10),

("name3","add3","city3",20))

是否有可能获得以上输出？

据我所知，distinct如果整个元组/值重复，则有效。我试过 distinct喜欢以下 :

val b = List(("name1","add1","city1",10),("name1","add1","city1",10),("name2","add2","city2",10),
("name2","add2","city2",20),("name3","add3","city3",20)).distinct

但它给出的输出为 -

List(("name1","add1","city1",10),("name2","add2","city2",10),
("name2","add2","city2",20),("name3","add3","city3",20))

任何替代方法也将不胜感激。

Answer 1

使用 groupBy像这样

a.groupBy( v => (v._1,v._2,v._3)).keys.toList

这构造了一个 Map其中每个键根据定义是上面 lambda 函数中要求的唯一三元组。

如果它还包含元组中的最后一个元素，则为每个键获取第一个元素，如下所示

a.groupBy( v => (v._1,v._2,v._3)).mapValues(_.head)