Option Strict On
Imports System
''' <summary>
''' Provides utility methods for finding distances between values in an array.
''' </summary>
Public NotInheritable Class ArrayDistance
' Prevent instantiation of this utility class.
Private Sub New()
End Sub
''' <summary>
''' Finds the minimum distance between two values in an array.
''' </summary>
''' <param name="numbers">The array to search.</param>
''' <param name="target1">The first target value.</param>
''' <param name="target2">The second target value.</param>
''' <returns>
''' The minimum distance between the two values,
''' or -1 if no matching pair exists.
''' </returns>
''' <exception cref="ArgumentNullException">
''' Thrown when numbers is Nothing.
''' </exception>
Public Shared Function FindMinimumDistance(numbers As Integer(), target1 As Integer, target2 As Integer) As Integer
If numbers Is Nothing Then
Throw New ArgumentNullException(NameOf(numbers))
End If
' Special case: both target values are the same.
If target1 = target2 Then
Return FindMinimumDistanceBetweenDuplicates(numbers, target1)
End If
Dim lastSeenIndex As Integer = -1
Dim minimumDistance As Integer = Integer.MaxValue
For currentIndex As Integer = 0 To numbers.Length - 1
Dim currentValue As Integer = numbers(currentIndex)
' Ignore values that are not one of the targets.
If currentValue <> target1 AndAlso currentValue <> target2 Then
Continue For
End If
'
' If we previously found one target and the current
' value is the other target, update the minimum distance.
'
If lastSeenIndex >= 0 AndAlso
currentValue <> numbers(lastSeenIndex) Then
Dim distance As Integer = currentIndex - lastSeenIndex
minimumDistance = Math.Min(minimumDistance, distance)
End If
' Store the most recent index.
lastSeenIndex = currentIndex
Next
Return If(
minimumDistance = Integer.MaxValue,
-1,
minimumDistance)
End Function
''' <summary>
''' Finds the minimum distance between consecutive occurrences
''' of the same value.
''' </summary>
Private Shared Function FindMinimumDistanceBetweenDuplicates(numbers As Integer(), target As Integer) As Integer
Dim previousIndex As Integer = -1
Dim minimumDistance As Integer = Integer.MaxValue
For i As Integer = 0 To numbers.Length - 1
If numbers(i) <> target Then
Continue For
End If
If previousIndex >= 0 Then
Dim distance As Integer = i - previousIndex
minimumDistance = Math.Min(minimumDistance, distance)
End If
previousIndex = i
Next
Return If(
minimumDistance = Integer.MaxValue,
-1,
minimumDistance)
End Function
End Class
Module Program
Sub Main()
Dim numbers As Integer() = {2, 3, 7, 3, 3, 4, 8, 8, 8, 11, 9, 1, 3}
Dim result As Integer = ArrayDistance.FindMinimumDistance(numbers, 3, 8)
If result >= 0 Then
Console.WriteLine($"Minimum distance between 3 and 8: {result}")
Else
Console.WriteLine("No valid pair found.")
End If
End Sub
End Module
' run:
'
' Minimum distance between 3 and 8: 2
'
