Scala 如何计算列表中出现的次数 [英] Scala how can I count the number of occurrences in a list

问题描述

val list = List(1,2,4,2,4,7,3,2,4)

我想这样实现:list.count(2)(返回 3).

I want to implement it like this: list.count(2) (returns 3).

推荐答案

其他答案的一个更简洁的版本是:

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)

给出一个Map，其中包含原始序列中每个项目的计数:

giving a Map with a count for each item in the original sequence:

Map(banana -> 1, oranges -> 3, apple -> 3)

该问题询问如何查找特定项目的计数.使用这种方法，解决方案需要将所需元素映射到其计数值，如下所示:

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")

这篇关于Scala 如何计算列表中出现的次数的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！