Please write an algorithm no need for code

Question

You are given a file called “std” and composed of “Number, Name, Address” fields. Write an algorithm that makes “insert, delete, update and retrieve”, processes on the records in the file. The “Number” field is the key of each record.

Answer 1

Structure _TDataRec

Public recNum As Integer

Public name As String

Public address As String

End Structure

Public Sub Parse(ByRef dataRec As _TDataRec, inbuff As String)

Dim tokens() As String = inbuff.Split(",")

dataRec.recNum = Val(tokens(0).Trim())

dataRec.name = tokens(1)

dataRec.address = tokens(2)

End Sub

Public Function SerializeToCSV(dataRec As _TDataRec)

Dim outbuff As String

outbuff = Str(dataRec.recNum) & "," & dataRec.name & "," & dataRec.address

SerializeToCSV = outbuff

End Function

Public Sub Dump(dataRec As _TDataRec, strMsg As String)

If (Not IsNothing(strMsg)) Then

Console.WriteLine("************************************")

Console.WriteLine(strMsg)

End If

Console.WriteLine("**********************************************")

Console.WriteLine(" rec # = " & dataRec.recNum)

Console.WriteLine(" name = >" & dataRec.name & "<")

Console.WriteLine(" address = >" & dataRec.address & "<")

End Sub

Structure _TDbTable

Public dataRecs() As _TDataRec

Public numDataRecs As Integer

End Structure

Public Sub DBTable_Init(ByRef db As _TDbTable)

ReDim db.dataRecs(1)

db.numDataRecs = 0

End Sub

Public Sub InsertAddNew(ByRef db As _TDbTable, newDataRec As _TDataRec)

If (db.numDataRecs = 0) Then

db.dataRecs(0) = newDataRec

db.numDataRecs = 1

Else

db.numDataRecs = db.numDataRecs + 1

ReDim Preserve db.dataRecs(db.numDataRecs)

db.dataRecs(db.numDataRecs - 1) = newDataRec

End If

End Sub

Public Sub DeleteRemove(ByRef db As _TDbTable, iIndexPos As Integer)

If (iIndexPos >= 0 And iIndexPos < db.numDataRecs) Then

For iLoop = iIndexPos To db.numDataRecs - 1

db.dataRecs(iLoop) = db.dataRecs(iLoop + 1)

Next

db.numDataRecs = db.numDataRecs - 1

ReDim Preserve db.dataRecs(db.numDataRecs)

End If

End Sub

Public Sub Update(ByRef db As _TDbTable, iIndexPos As Integer, dataRec As _TDataRec)

If (iIndexPos >= 0 And iIndexPos < db.numDataRecs) Then

db.dataRecs(iIndexPos) = dataRec

End If

End Sub

Public Sub IndexerGetAtIndex(db As _TDbTable, iIndexPos As Integer, ByRef dataRec As _TDataRec)

'deep copies: always return COPY to the caller, not the address; caller CANNOT change original

If (iIndexPos >= 0 And iIndexPos < db.numDataRecs) Then

dataRec.recNum = db.dataRecs(iIndexPos).recNum

dataRec.name = db.dataRecs(iIndexPos).name

dataRec.address = db.dataRecs(iIndexPos).address

End If

End Sub

Public Sub ReadFile(filename As String, ByRef db As _TDbTable)

On Error GoTo ErrHandler

Dim curDataRec As _TDataRec

Dim fileReader As System.IO.StreamReader

Dim stringReader As String = "?"

db.numDataRecs = 0

fileReader = My.Computer.FileSystem.OpenTextFileReader(filename)

curDataRec = Nothing

While True

stringReader = fileReader.ReadLine()

If IsNothing(stringReader) Then

Exit While

End If

Parse(curDataRec, stringReader)

InsertAddNew(db, curDataRec)

End While

fileReader.Close()

ErrHandler:

Console.WriteLine("Error opening/reading file ")

Return

End Sub

Public Sub WriteFile(filename As String, ByRef db As _TDbTable)

On Error GoTo ErrHandler

Dim curDataRec As _TDataRec

Dim fileWriter As System.IO.StreamWriter

Dim outbuff As String

fileWriter = My.Computer.FileSystem.OpenTextFileWriter(filename, False)

For iLoop = 0 To db.numDataRecs - 1

outbuff = SerializeToCSV(db.dataRecs(iLoop))

fileWriter.WriteLine(outbuff)

Next

fileWriter.Close()

ErrHandler:

Console.WriteLine("Error opening/writing file ")

Return

End Sub