如何计算字符串的字符？ [英] How to count characters of a String?

问题描述

我是Scala的新手！我想计算一个字符串中出现char的次数。我该怎么做呢？我开始写这样的东西，但是我发现语法很难掌握。有帮助吗？

I am a pretty newbie to Scala! I would like to count the times a char occurs in a string. How do I do this? I started writing something like this but I find the syntax very hard to grasp. Any help?

 var s = "hello"
 var list = s.toList.distinct
 list.foreach(println(s.count(_=='list')))

推荐答案

如果您想要将字符映射到计数，可以尝试执行以下操作：

You could try something like this if you wanted a Map of the chars to the counts:

val str = "hello"
val countsMap:Map[Char,Int] = 
  str.
    groupBy(identity).
    mapValues(_.size)

将扩展为更长的形式：

str.
  groupBy(c => c).
  mapValues(str => str.size)

因此， groupBy 我们是说我们要按字符串本身中的各个 Char s分组。这样会产生一个 Map [Char，String] ，像这样：

So to break this down, in the groupBy we are saying that we want to group by the individual Chars in the String themselves. This will produce a Map[Char, String] like so:

Map(e -> e, h -> h, l -> ll, o -> o)

然后，使用 mapValues 方法重新映射 Map 的值部分使用 String 的 .size 而不是 String 本身。

Then, you re-map the values portion of that Map with the mapValues method telling it to use the .size of the String and not the String itself.

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