Scala how can I count the number of occurrences in a list
val list = List(1,2,4,2,4,7,3,2,4)
我想要像这样实现它： list.count(2) （返回3）。
A somewhat cleaner version of one of the other answers is:
val s = Seq("apple", "oranges", "apple", "banana", "apple", "oranges", "oranges")
s.groupBy(identity).mapValues(_.size)
giving a Map with a count for each item in the original sequence:
Map(banana -> 1, oranges -> 3, apple -> 3)
The question asks how to find the count of a specific item. With this approach, the solution would require mapping the desired element to its count value as follows:
s.groupBy(identity).mapValues(_.size)("apple")
斯卡拉集合确实有count ： list.count(_ == 2)
I had the same problem as Sharath Prabhal, and I got another (to me clearer) solution :
val s = Seq("apple", "oranges", "apple", "banana", "apple", "oranges", "oranges")
s.groupBy(l => l).map(t => (t._1, t._2.length))
With as result :
Map(banana -> 1, oranges -> 3, apple -> 3)
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