The Selection Sorting Algorithm in VBScript

The selection sort, similar to insertion sort, is one of the simple sorting algorithm that has O(N^2) time complexity. The selection sorting algorithm is quadratic, thus not efficient when the items to sort is large.

The selection sort works by choosing a minimal element in the unsorted list and append the element to the sorted list – which is done by swapping the element beyond the end of the sorted part.

For example, given the array: [3, 5, 2, 6, 1, 3, 4, 6, 9], we can simulate the Selection Sort algorithm in the following process:

Sorted: [] Unsorted: [3, 5, 2, 6, 1, 3, 4, 6, 9] // min = 1 in the Unsorted
Sorted: [1, ] Unsorted: [3, 5, 2, 6, 3, 4, 6, 9] // min = 2 in the Unsorted
Sorted: [1, 2] Unsorted: [3, 5, 6, 3, 4, 6, 9] // min = 3 in the Unsorted
Sorted: [1, 2, 3] Unsorted: [5, 6, 3, 4, 6, 9] // min = 3 in the Unsorted
Sorted: [1, 2, 3, 3] Unsorted: [5, 6, 4, 6, 9] // min = 4 in the Unsorted
Sorted: [1, 2, 3, 3, 4] Unsorted: [5, 6, 6, 9] // min = 5 in the Unsorted
Sorted: [1, 2, 3, 3, 4, 5] Unsorted: [6, 6, 9] // min = 6 in the Unsorted
Sorted: [1, 2, 3, 3, 4, 5, 6] Unsorted: [6, 9] // min = 6 in the Unsorted
Sorted: [1, 2, 3, 3, 4, 5, 6, 6] Unsorted: [9] // min = 9 in the Unsorted
Sorted: [1, 2, 3, 3, 4, 5, 6, 6, 9] Unsorted: [] // Done.

Translating to VBScript, we have the following Selection Sorting Algorithm:

Dim Nums: Nums = Array(3, 5, 2, 6, 1, 3, 4, 6, 9)

Sub SelectionSort(ByRef Nums)
	For i = LBound(Nums) To UBound(Nums) - 1
		Dim min: min = i
		For j = i + 1 To UBound(Nums)
			If Nums(j) < Nums(min) Then
				min = j
			End If 
		Next
		If min <> i Then
			Dim t: t = Nums(min)
			Nums(min) = Nums(i)
			Nums(i) = t
		End If
	Next
End Sub

SelectionSort Nums
For i = LBound(Nums) To UBound(Nums) 
	WScript.Echo Nums(i)
Next

One advantage of Selection Sorting Algorithm is that it has at most (n-1) swaps when sorting n elements.

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