Question

How to write a recursive function to generate all permutations of a string in Scala

Answer 1

object PermuteString {

  def swap(str: String, i: Int, j: Int): String = {
    val chars = str.toCharArray
    val temp = chars(i)
    
    chars(i) = chars(j)
    chars(j) = temp
    
    new String(chars)
  }

  def generatePermutation(str: String, l: Int, r: Int): Unit = {
    if (l == r) {
      println(str)
    } else {
      for (i <- l to r) {
        val swapped = swap(str, l, i)
        generatePermutation(swapped, l + 1, r)
      }
    }
  }

  def main(args: Array[String]): Unit = {
    val s = "ABC"
    
    generatePermutation(s, 0, s.length - 1)
  }
}




/*
run:

ABC
ACB
BAC
BCA
CBA
CAB

*/

 

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