我有一个Scala函数,它在整个生命周期中执行2-3次递归调用。我想将变量保存在列表中的第二个元组中。有没有一种聪明的方法可以做到这一点?
仅仅传递变量就意味着我将拥有一个ListString,而实际上我想要的是一个List[ListString]。
函数内部是否需要一个随每次迭代而更新的变量?
def someRecursiveFunction(listOfWords:List[String])List[List[String]] = {
val textSplitter = listOfWords.lastIndexOf("Some Word")
if (Some Word != -1) {
val someTuple = listofWords.splitAt(textSplitter)
val valueIwant = someTuple._2
someRecursiveFunction(someTuple._1)
}
List(someTuple._2,someTuple._2(1),someTuple._2(2)) // What I want back
}有没有办法从递归函数中提取出第二个元组,以便我可以在程序中进一步使用它?
发布于 2018-09-26 01:42:39
如果返回类型固定为List[List[String]],则需要对代码进行以下更改:
someType._2是作为someType._2(2)访问的,所以someType._2列表中至少应该有3字符串。List[List[String]]。因为someType._2(1)和someType._2(2)只是字符串而不是List[String]:List(someTuple._2,List(someTuple._2(1),someTuple._2(2)))将是返回类型,值"Some Word“将在递归过程中改变,注意到someTuple._2.size总是>=3.someType._2,它将在每次递归过程中改变,它在递归函数中被声明为var。有了从您的需求中得出的理解,下面的代码可能就是您正在寻找的代码:
def someRecursiveFunction(listOfWords:ListString,sw: String):List[ListString] ={ val textSplitter = listOfWords.lastIndexOf(sw) var i =0 if(i==0) { var someTuple:(ListString,ListString) = (List(),List()) } if (textSplitter != -1 && listOfWords.size-3>=textSplitter) { someTuple = listOfWords.splitAt(textSplitter) println(someTuple._1,someTuple._2) //用于检查递归if( someTuple._1.size>=3){ i+=1 someRecursiveFunction(someTuple._1,someTuple._1(textSplitter-3))} } List(someTuple._2,List(someTuple._2(1),someTuple._2(2) // What I want back }
Scala中的:
val list = List("a","b","c","x","y","z","k","j","g","Some Word","d","e","f","u","m","p")
scala> val list = List("a","b","c","x","y","z","k","j","g","Some Word","d","e","f","u","m","p")
list: List[String] = List(a, b, c, x, y, z, k, j, g, Some Word, d, e, f, u, m, p)
scala> someRecursiveFunction(list,"d")
(List(a, b, c, x, y, z, k, j, g, Some Word),List(d, e, f, u, m, p))
(List(a, b, c, x, y, z, k),List(j, g, Some Word))
(List(a, b, c, x),List(y, z, k))
(List(a),List(b, c, x))
res70: List[List[String]] = List(List(b, c, x), List(c, x))
scala> someRecursiveFunction(list,"Some Word")
(List(a, b, c, x, y, z, k, j, g),List(Some Word, d, e, f, u, m, p))
(List(a, b, c, x, y, z),List(k, j, g))
(List(a, b, c),List(x, y, z))
(List(),List(a, b, c))
res71: List[List[String]] = List(List(a, b, c), List(b, c))https://stackoverflow.com/questions/52466576
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