Scala：刪除最後一次出現的字符

Question

我想刪除字符串中最後一次出現的字符。我可以得到它的index：對字符串

str.lastIndexOf(',') 

我已經嘗試使用split和replace功能。

Answer 1

你可以使用patch。

scala> val s = "s;dfkj;w;erw" 
s: String = s;dfkj;w;erw 

scala> s.patch(s.lastIndexOf(';'), "", 1) 
res6: String = s;dfkj;werw 

Answer 2

你可以嘗試以下方法：

val input = "The quick brown fox jumps over the lazy dog" 
val lastIndexOfU = input.lastIndexOf("u") 
val splits = input.splitAt(lastIndexOfU) 
val inputWithoutLastU = splits._1 + splits._2.drop(1) // "The quick brown fox jmps over the lazy dog" 

Answer 3

scala> def removeLast(x: Char, xs: String): String = { 
    | 
    | val accumulator: (Option[Char], String) = (None, "") 
    | 
    | val (_, applied) = xs.foldRight(accumulator){(e: Char, acc: (Option[Char], String)) => 
    |  val (alreadyReplaced, runningAcc) = acc 
    |  alreadyReplaced match { 
    |   case some @ Some(_) => (some, e + runningAcc) 
    |   case None   => if (e == x) (Some(e), runningAcc) else (None, e + runningAcc) 
    |   } 
    | } 
    | 
    | applied 
    | } 
removeLast: (x: Char, xs: String)String 

scala> removeLast('f', "foobarf") 
res7: String = foobar 

scala> removeLast('f', "foobarfff") 
res8: String = foobarff