Question

How to find first and last positions of an element in a sorted array in VB.NET

Answer 1

Imports System

Public Class Test
    Public Shared Sub find_first_and_Last_position(arr() As Integer, n As Integer)  
        Dim first As Integer = -1
        Dim last As Integer = -1
        
        For i As Integer = 0 to arr.Length - 1
            If n <> arr(i) Then
                Continue For 
            End If
            If first = -1 Then
                first = i
            End If
            last = i
        Next
        If first <> -1 Then 
            Console.WriteLine("First positions = {0} Last positions = {1}", first, last)
        else
            Console.Write("Not Found")
        End If
    End Sub
    
    Public Shared Sub Main()
        Dim arr() As Integer = {1, 3, 7, 8, 3, 1, 9}
        Dim n As Integer = 3
         
        find_first_and_Last_position(arr, n)
    End Sub
End Class



' run:
' 
' First positions = 1 Last positions = 4
'

 

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Answer 2

Imports System

Public Class Test
    Public Shared Sub find_first_and_Last_position(arr() As Integer, n As Integer, ByRef first As Integer, ByRef last As Integer)
        first = -1
        last = -1
        
        For i As Integer = 0 to arr.Length - 1
            If n <> arr(i) Then
                Continue For 
            End If
            If first = -1 Then
                first = i
            End If
            last = i
        Next

    End Sub
    
    Public Shared Sub Main()
        Dim arr() As Integer = {1, 3, 7, 8, 3, 1, 9}
        Dim n As Integer = 3
        Dim first As Integer
        Dim last As Integer
         
        find_first_and_Last_position(arr, n, first, last)
        
        If first <> -1 Then 
            Console.WriteLine("First positions = {0} Last positions = {1}", first, last)
        else
            Console.Write("Not Found")
        End If
    End Sub
End Class



' run:
' 
' First positions = 1 Last positions = 4
'

 

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