Scala language implementation of Selection Sort

Introduction

Selection sort is the simplest sorting algorithm in terms of implementation.
Let's consider we have a list of elements i.e. {3, 9, 0, 5, 4 }

a) Selection sort maintains two sublists, one sorted and initially empty and second unsorted sublist i.e.
[ {}, {3, 9 , 0, 5 ,4 }]

b) It searches for the minimum element (for ascending sort) OR for a maximum element( for descending sort) in the unsorted list in each step.

Step 1

[ {0 }, {9,3,5,4}]
Minimum element = 0 , swapped with 3

Step 2

Minimum element = 3 , swapped with 9
[{0,3) , {9,5,4} ]

Step 3

Minimum element = 4 , swapped with 9
[{0,3,4} , {5,9}]

Step 4

Minimum element = 5 , swapped with itself
[{0,3,4,5}, {9}]

Step 5

Minimum element = 9 , swapped with itself
[{0,3,4,5,9}, {}]

Worst Complexity: O(n*n)

Best Complexity   : O(n * n)

Implementation

package main.scala

object SelectionSort {

  val array = Array(0, 5, 2, 6, 3, 1)

  def main(args: Array[String]) {
    print("Unsorted List ")
    println(array.toList)
    print("Asceding sorted List ")
    sortAscending;
    println(array.toList)

    sortDescending
    print("Desceding sorted List ")
    println(array.toList)
  }

  def sortAscending {
    for (outer <- 0 until array.length) {
      var minimumIndex = outer;
      for (inner <- outer + 1 until array.length) {
        if (array.apply(minimumIndex) > array.apply(inner)) {
          minimumIndex = inner
        }
      }
      swap(minimumIndex, outer)
    }
  }

  def sortDescending {
    for (outer <- 0 until array.length) {
      var maximumIndex = outer;
      for (inner <- outer + 1 until array.length) {
        if (array.apply(maximumIndex) < array.apply(inner)) {
          maximumIndex = inner
        }
      }
      swap(maximumIndex, outer)
    }
  }

  def swap(minimumIndex: Int, swapIndex: Int) {
    var temp = array.apply(minimumIndex)
    array.update(minimumIndex, array.apply(swapIndex))
    array.update(swapIndex, temp)
  }
}

Input   : 3,9, 0, 5 ,4
Output: 0 3 4 5 9 (Ascending)
Output: 9 5 4 3 0 (Descending)

Conclusion

In this tutorial, we learned how to implement Selection Sort using Scala language. Please leave your comments in the comment box. Happy learning :)