A Level Linked List | C# Online Compiler

A Level Linked List by Mr Raja

Imports System
'====================================================================================
Public Module Module1
    Sub Main()
        Dim Choice As Char
        Dim Data As String
        Dim CurrentNodePtr As Integer
        InitialiseList()
        Choice = GetOption()
        Do While Choice <> "5"
            Select Case Choice
                Case "1"
 					Console.Write("Enter the value: ")
					Data = Console.ReadLine()
					AddNode(Data)
					OutputAllNodes()
				Case "2"
					Console.Write("Enter the value: ")
					Data = Console.ReadLine()
					DeleteNode(Data)
					OutputAllNodes()
				Case "3"
					Console.Write("Enter the value: ")
					Data = Console.ReadLine()
				CurrentNodePTr = SearchNode(Data)
					Console.WriteLine("Pointer: " & SearchNode(Data))
				Case "4"
					OutputAllNodes()
			End Select
			Console.WriteLine("Press any key to continue...")
			Console.ReadLine()
			Console.Clear()
            Choice = GetOption()
		Loop 
	End Sub	
'====================================================================================

    Function GetOption()
        Dim Choice As Char
		Console.WriteLine("==========================")
		Console.WriteLine("     Linked List Menu")
		Console.WriteLine("==========================")
		Console.WriteLine("Press  1: Add")
		Console.WriteLine("       2: Delete")
		Console.WriteLine("       3: Search")
		Console.WriteLine("       4: Display List")
		Console.WriteLine("       5: Exit")
		Console.WriteLine("==========================")
        Console.Write("Enter your choice: ")
        Choice = Console.ReadLine()
        Return (Choice)
	End Function	
'====================================================================================
    ' NullPointer should be set to -1 if using array element with index 0
    Const NULLPOINTER = -1
	
    ' Declare record type to store data and pointer
    Structure ListNode
		Dim Data As String
        Dim Pointer As Integer
    End Structure

    Dim List(7) As ListNode
    Dim StartPointer As Integer
    Dim FreeListPtr As Integer
'====================================================================================
    Sub InitialiseList()
        StartPointer = NULLPOINTER 'set start pointer
        FreeListPtr = 1 'set starting position of free list
        'link all nodes to make free list
		For Index = 0 To List.Length - 1
			List(Index).Pointer = Index + 1
		Next
		List(List.Length - 1).Pointer = NULLPOINTER 'last node of free list 
	End Sub
'====================================================================================
    Sub AddNode(NewItem)
	Dim ThisNodePtr, NewNodeIndex, PreviousNodePtr As Integer
			If FreeListPtr <> NULLPOINTER Then  ' check there is space in the array
			' take node from free list and store data item
			NewNodeIndex = FreeListPtr
			List(NewNodeIndex).Data = NewItem
			FreeListPtr = List(FreeListPtr).Pointer  ' Can be [FreeListPtr = List(NewNodeIndex).Pointer]
			' find insertion point
			PreviousNodePtr = NULLPOINTER
			' start at beginning
			ThisNodePtr = StartPointer

			Try		' while not end of list
				Do While (ThisNodePtr <> NULLPOINTER) And (List(ThisNodePtr).Data < NewItem)
						PreviousNodePtr = ThisNodePtr ' remember this node
						' follow the pointer to the next node
						ThisNodePtr = List(ThisNodePtr).Pointer
				Loop
			Catch ex As Exception
			End Try

			If PreviousNodePtr = NULLPOINTER Then ' insert new node at start of list
				List(NewNodeIndex).Pointer = StartPointer
				StartPointer = NewNodeIndex
			Else  ' insert new node between previous node and this node
				List(NewNodeIndex).Pointer = List(PreviousNodePtr).Pointer
					List(PreviousNodePtr).Pointer = NewNodeIndex
			End If
		Else
            console.writeline("no space for more data")
        End If
	End Sub
'====================================================================================
	'returns pointer to node
    Function SearchNode(DataItem) As Integer 
        Dim CurrentNodePtr As Integer
        CurrentNodePtr = StartPointer  'start at beginning of list
        Try
			'not end of list and item not found
            Do While CurrentNodePtr <> NULLPOINTER And List(CurrentNodePtr).Data <> DataItem
                'follow the pointer to the next node
				'Console.WriteLine("CurrentNodePtr: " & CurrentNodePtr)
				Console.WriteLine(CurrentNodePtr)
                CurrentNodePtr = List(CurrentNodePtr).Pointer
            Loop
        Catch ex As Exception
            Console.WriteLine("data not found")
			Console.WriteLine(ex)
        End Try
        Return (CurrentNodePtr)  ' returns NullPointer if item not found
	End Function
'====================================================================================
    Sub DeleteNode(DataItem)
        Dim ThisNodePtr, PreviousNodePtr As Integer
        ThisNodePtr = StartPointer 'start at beginning of list
        Try
			' while not end of list and item not found
            Do While ThisNodePtr <> NULLPOINTER And List(ThisNodePtr).Data <> DataItem
                PreviousNodePtr = ThisNodePtr    ' remember this node
				' follow the pointer to the next node
                ThisNodePtr = List(ThisNodePtr).Pointer
            Loop
        Catch ex As Exception
            Console.WriteLine("data does not exist in list")
        End Try
        If ThisNodePtr <> NULLPOINTER Then ' node exists in list
            If ThisNodePtr = StartPointer Then ' first node to be deleted
                StartPointer = List(StartPointer).Pointer
			Else
                List(PreviousNodePtr).Pointer = List(ThisNodePtr).Pointer
			End If
            List(ThisNodePtr).Pointer = FreeListPtr
            FreeListPtr = ThisNodePtr
		End If 
	End Sub
'====================================================================================
    Sub OutputAllNodes()
        Dim CurrentNodePtr As Integer
        CurrentNodePtr = StartPointer ' start at beginning of list
        If StartPointer = NULLPOINTER Then
			Console.Clear()
			Console.WriteLine("==========================")
	 		Console.WriteLine("|     No data in list    |")
			Console.WriteLine("==========================")
		Else
		Console.Clear()
		Console.WriteLine("===========================")
		Console.WriteLine("| Index | Value | Pointer |")
		Console.WriteLine("===========================")
        Do While CurrentNodePtr <> NULLPOINTER ' while not end of list
            Console.WriteLine(CurrentNodePtr & "          " & List(CurrentNodePtr).Data & "        " & List(CurrentNodePtr).Pointer)
            ' follow the pointer to the next node
            CurrentNodePtr = List(CurrentNodePtr).Pointer
		Loop 
		End If
	End Sub
'====================================================================================
End Module

​x
 
Imports System
'====================================================================================
Public Module Module1
    Sub Main()
        Dim Choice As Char
        Dim Data As String
        Dim CurrentNodePtr As Integer
        InitialiseList()
        Choice = GetOption()
        Do While Choice <> "5"
            Select Case Choice
                Case "1"
                    Console.Write("Enter the value: ")
                    Data = Console.ReadLine()
                    AddNode(Data)
                    OutputAllNodes()
                Case "2"
                    Console.Write("Enter the value: ")
                    Data = Console.ReadLine()
                    DeleteNode(Data)
                    OutputAllNodes()
                Case "3"
                    Console.Write("Enter the value: ")
                    Data = Console.ReadLine()
                CurrentNodePTr = SearchNode(Data)
                    Console.WriteLine("Pointer: " & SearchNode(Data))
                Case "4"
                    OutputAllNodes()
            End Select
            Console.WriteLine("Press any key to continue...")
            Console.ReadLine()
            Console.Clear()
            Choice = GetOption()
        Loop 
    End Sub 
'====================================================================================
​
    Function GetOption()
        Dim Choice As Char
        Console.WriteLine("==========================")
        Console.WriteLine("     Linked List Menu")
        Console.WriteLine("==========================")
        Console.WriteLine("Press  1: Add")
        Console.WriteLine("       2: Delete")
        Console.WriteLine("       3: Search")
        Console.WriteLine("       4: Display List")
        Console.WriteLine("       5: Exit")
        Console.WriteLine("==========================")
        Console.Write("Enter your choice: ")
        Choice = Console.ReadLine()
        Return (Choice)
    End Function    
'====================================================================================
    ' NullPointer should be set to -1 if using array element with index 0
    Const NULLPOINTER = -1
    
    ' Declare record type to store data and pointer
    Structure ListNode
        Dim Data As String
        Dim Pointer As Integer
    End Structure
​
    Dim List(7) As ListNode
    Dim StartPointer As Integer
    Dim FreeListPtr As Integer
'====================================================================================
    Sub InitialiseList()
        StartPointer = NULLPOINTER 'set start pointer
        FreeListPtr = 1 'set starting position of free list
        'link all nodes to make free list
        For Index = 0 To List.Length - 1
            List(Index).Pointer = Index + 1
        Next
        List(List.Length - 1).Pointer = NULLPOINTER 'last node of free list 
    End Sub
'====================================================================================
    Sub AddNode(NewItem)
    Dim ThisNodePtr, NewNodeIndex, PreviousNodePtr As Integer
            If FreeListPtr <> NULLPOINTER Then  ' check there is space in the array
            ' take node from free list and store data item
            NewNodeIndex = FreeListPtr
            List(NewNodeIndex).Data = NewItem
            FreeListPtr = List(FreeListPtr).Pointer  ' Can be [FreeListPtr = List(NewNodeIndex).Pointer]
            ' find insertion point
            PreviousNodePtr = NULLPOINTER
            ' start at beginning
            ThisNodePtr = StartPointer
​
            Try     ' while not end of list
                Do While (ThisNodePtr <> NULLPOINTER) And (List(ThisNodePtr).Data < NewItem)
                        PreviousNodePtr = ThisNodePtr ' remember this node
                        ' follow the pointer to the next node
                        ThisNodePtr = List(ThisNodePtr).Pointer
                Loop
            Catch ex As Exception
            End Try
​
            If PreviousNodePtr = NULLPOINTER Then ' insert new node at start of list
                List(NewNodeIndex).Pointer = StartPointer
                StartPointer = NewNodeIndex
            Else  ' insert new node between previous node and this node
                List(NewNodeIndex).Pointer = List(PreviousNodePtr).Pointer
                    List(PreviousNodePtr).Pointer = NewNodeIndex
            End If
        Else
            console.writeline("no space for more data")
        End If
    End Sub
'====================================================================================
    'returns pointer to node
    Function SearchNode(DataItem) As Integer 
        Dim CurrentNodePtr As Integer
        CurrentNodePtr = StartPointer  'start at beginning of list
        Try
            'not end of list and item not found
            Do While CurrentNodePtr <> NULLPOINTER And List(CurrentNodePtr).Data <> DataItem
                'follow the pointer to the next node
                'Console.WriteLine("CurrentNodePtr: " & CurrentNodePtr)
                Console.WriteLine(CurrentNodePtr)
                CurrentNodePtr = List(CurrentNodePtr).Pointer
            Loop
        Catch ex As Exception
            Console.WriteLine("data not found")
            Console.WriteLine(ex)
        End Try
        Return (CurrentNodePtr)  ' returns NullPointer if item not found
    End Function
'====================================================================================
    Sub DeleteNode(DataItem)
        Dim ThisNodePtr, PreviousNodePtr As Integer
        ThisNodePtr = StartPointer 'start at beginning of list
        Try
            ' while not end of list and item not found
            Do While ThisNodePtr <> NULLPOINTER And List(ThisNodePtr).Data <> DataItem
                PreviousNodePtr = ThisNodePtr    ' remember this node
                ' follow the pointer to the next node
                ThisNodePtr = List(ThisNodePtr).Pointer
            Loop
        Catch ex As Exception
            Console.WriteLine("data does not exist in list")
        End Try
        If ThisNodePtr <> NULLPOINTER Then ' node exists in list
            If ThisNodePtr = StartPointer Then ' first node to be deleted
                StartPointer = List(StartPointer).Pointer
            Else
                List(PreviousNodePtr).Pointer = List(ThisNodePtr).Pointer
            End If
            List(ThisNodePtr).Pointer = FreeListPtr
            FreeListPtr = ThisNodePtr
        End If 
    End Sub
'====================================================================================
    Sub OutputAllNodes()
        Dim CurrentNodePtr As Integer
        CurrentNodePtr = StartPointer ' start at beginning of list
        If StartPointer = NULLPOINTER Then
            Console.Clear()
            Console.WriteLine("==========================")
            Console.WriteLine("|     No data in list    |")
            Console.WriteLine("==========================")
        Else
        Console.Clear()
        Console.WriteLine("===========================")
        Console.WriteLine("| Index | Value | Pointer |")
        Console.WriteLine("===========================")
        Do While CurrentNodePtr <> NULLPOINTER ' while not end of list
            Console.WriteLine(CurrentNodePtr & "          " & List(CurrentNodePtr).Data & "        " & List(CurrentNodePtr).Pointer)
            ' follow the pointer to the next node
            CurrentNodePtr = List(CurrentNodePtr).Pointer
        Loop 
        End If
    End Sub
'====================================================================================
End Module

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