how to switch two letters in a string?

I want to switch the order of the letters. For example, there is a string "abc" and the output must be "bac". Can you please tell me how I can do it?

Thank you in adv开发者_如何学JAVAance.

You can use fact, that String can be converted to IndexedSeq[Char] implicitly:

def switch(s: String) = (s take 2 reverse) + (s drop 2)

This function also works correctly with strings, that smaller than 2 chars, just try this:

println(switch("abc")) // prints: bac
println(switch("ab")) // prints: ba
println(switch("a")) // prints: a
println(switch("")) // prints: 

Your question is not clear as to whether you want something which reverses a String, or whether you want something which swaps two characters in a String. This answer is for the latter

def swap(s : String, idx1 : Int, idx2 : Int) : String = {
  val cs = s.toCharArray
  val swp = cs(idx1)
  cs(idx1) = cs(idx2)
  cs(idx2) = swp
  new String(cs)
}

Of course you could generalize this into anything which can be viewed as an IndexedSeq:

 def swap[A, Repr](repr : Repr, idx1 : Int, idx2 : Int)
     (implicit bf: CanBuildFrom[Repr, A, Repr], 
      ev : Repr <%< IndexedSeqLike[A, Repr]) : Repr = {
  val swp = repr(idx1)
  val n = repr.updated(idx1, repr(idx2))
  n.updated(idx2, swp)
}

How about something more functional?

import collection.breakOut

def swap(s:String, x:Int, y:Int):String = s.zipWithIndex.collect{
  case (_,`x`) => s(y)
  case (_,`y`) => s(x)
  case (c,_) => c
}(breakOut)