将字符串拆分为组 [英] Splitting string into groups

问题描述

我正在尝试将一个字符串分组"成段，我想这个例子会更简洁地解释它

I'm trying to 'group' a string into segments, I guess this example would explain it more succintly

scala> val str: String = "aaaabbcddeeeeeeffg"
... (do something)
res0: List("aaaa","bb","c","dd","eeeee","ff","g")

我可以想到几种以命令式风格执行此操作的方法(使用 vars 并逐步遍历字符串以查找组)，但我想知道是否有更好的功能解决方案可以能达到吗?我一直在浏览 Scala API，但似乎没有适合我需要的东西.

I can thnk of a few ways to do this in an imperative style (with vars and stepping through the string to find groups) but I was wondering if any better functional solution could be attained? I've been looking through the Scala API but there doesn't seem to be something that fits my needs.

任何帮助将不胜感激

推荐答案

可以用span递归拆分字符串:

You can split the string recursively with span:

def s(x : String) : List[String] = if(x.size == 0) Nil else {
    val (l,r) = x.span(_ == x(0))
    l :: s(r) 
}

尾递归:

@annotation.tailrec def s(x : String, y : List[String] = Nil) : List[String] = {
    if(x.size == 0) y.reverse 
    else {
        val (l,r) = x.span(_ == x(0))
        s(r, l :: y)
    }
}

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