Imports System
Imports System.Collections.Generic
Module ClosestToZero
' Function to find the two elements whose sum is closest to zero
Sub FindClosestToZero(lst As List(Of Integer))
If lst.Count < 2 Then
Console.WriteLine("list must have at least two elements.")
Return
End If
' Step 1: Sort the list
Dim sortedlst As New List(Of Integer)(lst)
sortedlst.Sort()
Dim left As Integer = 0
Dim right As Integer = sortedlst.Count - 1
Dim closestSum As Integer = Integer.MaxValue
Dim closestPair(1) As Integer
' Step 2: Use two-indexes technique
While left < right
Dim sum As Integer = sortedlst(left) + sortedlst(right)
' Update closest sum and pair if needed
If Math.Abs(sum) < Math.Abs(closestSum) Then
closestSum = sum
closestPair(0) = sortedlst(left)
closestPair(1) = sortedlst(right)
End If
' Move indexess
If sum < 0 Then
left += 1 ' Increase sum by moving left indexes
Else
right -= 1 ' Decrease sum by moving right indexes
End If
End While
' Output the result
Console.WriteLine("The two elements whose sum is closest to zero are: " &
closestPair(0) & " and " & closestPair(1) &
" with a sum of " & closestSum & ".")
End Sub
Sub Main()
Dim lst As New List(Of Integer) From {23, -26, -88, -42, 55, 99, -11, 90, -13, 17, -31}
FindClosestToZero(lst)
End Sub
End Module
' run:
'
' The two elements whose sum is closest to zero are: -88 and 90 with a sum of 2.
'
