漫遊於歷史與現代之間

普通版

Module Module1
    Sub Main()
        Dim x() As Integer = {0, 5, 6, 8, 9}
        Dim search, high, low, mid As Integer
        search = Console.ReadLine()
        low = 0
        high = 4
        mid = (low + high) / 2

        While (low <= high)
            If (x(mid) = search) Then
                Console.Write(mid)
                Exit While
            ElseIf (x(mid) > search) Then
                high = mid - 1
            ElseIf (x(mid) < search) Then
                low = mid + 1
            End If
            mid = (low + high) / 2
        End While

        If (x(mid) <> search) Then
            Console.Write(-1)
        End If

        Console.ReadKey()
    End Sub
End Module

遞迴版

Module Module1
    Dim x() As Integer = {0, 5, 6, 8, 9}

    Sub Main()
        Dim search, found As Integer
        search = Console.ReadLine
        found = bsearch(search, 0, 4)
        Console.Write(found)
        Console.ReadKey()
    End Sub

    Function bsearch(ByVal num As Integer, ByVal low As Integer, ByVal high As Integer)
        Dim mid As Integer
        If high < low Then
            bsearch = -1
        Else
            mid = (high + low) / 2
            If x(mid) = num Then
                bsearch = mid
            Else
                If x(mid) > num Then
                    high = mid - 1
                Else
                    low = mid + 1
                End If
                bsearch = bsearch(num, low, high)
            End If
        End If
    End Function

End Module