Computer Science 9618/43 May/June 2024: question paper and mark scheme

Mark scheme

1(a) 1 mark for: 1 Declaration of (global) array with identifier DataStored (Integer and 20 spaces) and NumberItems (Integer) e.g. Java public static Integer[] DataStored = new Integer[20]; public static Integer NumberItems= 0; VB.NET Dim DataStored(19) As Integer Dim NumberStored As Integer = 0 Python global DataStored #integer global NumberItems #Integer 20 items 1(b) 1 mark each 5 Procedure heading (and close where appropriate) with no parameter. Prompt/output of suitable message to request the input of the quantity of numbers and reading in quantity of numbers and storing/using … … each input in next space in DataStored e.g. Java public static void Initialise(){ Scanner scanner = new Scanner(System.in); Integer Quantity = 0; do{ System.out.println("How many numbers will you enter up to 20?"); Quantity = Integer.parseInt(scanner.nextLine()); }while(Quantity <= 0 || Quantity > 20); for(Integer X = 0; X < Quantity; X++){ System.out.println("Enter number"); DataStored[NumberItems] = Integer.parseInt(scanner.nextLine()); NumberItems++; VB.NET Sub Initialise() Console.WriteLine("How many numbers will you enter?") Dim Quantity As Integer Do Quantity = Console.ReadLine() Loop Until (Quantity > 0 And Quantity < 21) For Count = 0 To Quantity - 1 Console.WriteLine("Enter number") DataStored(NumberStored) = Console.ReadLine() NumberStored += 1 Next End Sub 1(b) Python def Initialise(): global DataStored global NumberItems Valid = False while(Valid == False): NumberItems = int(input("How many numbers will you enter?")) #loop until < 20 if NumberItems > 0 and NumberItems< 21: Valid = True for Count in range(0, NumberItems): DataStored.append(int(input("Enter number"))) 1(c)(i) 1 mark each: 2 Storing 0 in NumberItems and then calling Initialise() Outputting all contents of array DataStored e.g. Java public static Integer NumberItems= 0; Initialise(); for(Integer X = 0; X < NumberItems; X++){ System.out.println(DataStored[X]); VB.NET NumberItems = 0 Initialise() For X = 0 To NumberItems - 1 Console.WriteLine(DataStored(X)) Next Python NumberItems = 0 Initialise() print(DataStored) 1(c)(ii) 1 mark each 2 Output showing quantity entered twice (30 and 5) with first being invalid Array output 3 9 4 1 2 e.g. 1(d)(i) 1 mark each 4 Procedure header (and end where appropriate) and looping through each array element Working inner loop … …comparison of elements… …swapping of elements e.g. Java public static void BubbleSort(){ Integer Temp = 0; for(Integer Count = 0; Count < NumberItems; Count++){ for(Integer Count2 = 0; Count2 < NumberItems - 1; Count2++){ if(DataStored[Count2] > DataStored[Count]){ Temp = DataStored[Count2]; DataStored[Count2] = DataStored[Count]; DataStored[Count] = Temp; } } } } VB.NET Sub BubbleSort() Dim Temp As Integer For Count = 0 To NumberStored - 1 For Count2 = 0 To NumberStored - 2 If (DataStored(Count2) > DataStored(Count)) Then Temp = DataStored(Count) DataStored(Count) = DataStored(Count2) DataStored(Count2) = Temp End If Next Next End Sub 1(d)(i) Python def BubbleSort(): global DataStored global NumberItems for Count in range(0, NumberItems): for Count2 in range(0, NumberItems-1): if DataStored[Count2] > DataStored[Count]: DataStored[Count2], DataStored[Count] = DataStored[Count], DataStored[Count2] 1(d)(ii) 1 mark for calling BubbleSort() and outputting array contents after 1 e.g. VB.NET BubbleSort() For X = 0 To NumberStored - 1 Console.WriteLine(DataStored(X)) Next e.g. Java BubbleSort(); for(Integer X = 0; X < NumberItems; X++){ System.out.println(DataStored[X]); } e.g. Python BubbleSort() print(DataStored) 1(d)(iii) 1 mark for screenshot showing the inputs and the values in the correct order 1 e.g. 1(e)(i) 1 mark each 6 Function header BinarySearch taking DataToFind as a parameter Calculating the mid value (First + Last) \ 2 or equivalent inside loop Checking if the data at mid is the parameter and returning mid inside loop If DataToFind < mid, updating Last/Upper with mid – 1 inside loop If DataToFind > mid, updating First/Lower with mid + 1 inside loop Returning -1 when not found and a suitable loop with end criteria e.g. Java public static Integer BinarySearch(Integer DataToFind){ Integer MidValue = 0; Integer First = 0; Integer Last = NumberItems; while (First <= Last){ MidValue = (First + Last) / 2; if(DataToFind == DataStored[MidValue]){ return MidValue; } if(DataToFind < DataStored[MidValue]){ Last = MidValue - 1; }else{ First = MidValue + 1; } } return -1; } 1(e)(i) VB.NET Function BinarySearch(DataToFind) Dim First As Integer = 0 Dim Last As Integer = NumberItems Dim MidValue As Integer While (First <= Last) MidValue = (First + Last) / 2 If DataToFind = DataStored(MidValue) Then Return MidValue End If If DataToFind < DataStored(MidValue) Then Last = MidValue - 1 Else First = MidValue + 1 End If End While Return -1 End Function Python def BinarySearch(DataToFind): global DataStored global NumberItems First = 0 Last= NumberItems while(First <= Last): MidValue = int((First + Last) / 2) if DataToFind == DataStored[MidValue]: return MidValue if DataToFind < DataStored[MidValue]: Last = MidValue - 1 else: First = MidValue + 1 return -1 1(e)(ii) 1 mark each: 3 Taking number as input … calling BinarySearch with input Outputting value returned e.g. Java Scanner scanner = new Scanner(System.in); System.out.println("Enter a number to find"); Integer Search = Integer.parseInt(scanner.nextLine()); System.out.println(BinarySearch(Search)); VB.NET Console.WriteLine("Enter a number to find") Dim Search As Integer = Console.ReadLine() Console.WriteLine(BinarySearch(Search)) Python Search = int(input("Enter a number to find")) print(BinarySearch(Search)) 1(e)(iii) 1 mark for each test 2 e.g. Test 1 – Accept found in index 16 Test 2

Mark scheme

2(a)(i) 1 mark each to max 4 4 Class Tree declaration (and end where appropriate) All 5 attributes declared as private with correct identifiers and data types Constructor header (and end) taking 5 parameters Constructor assigns parameters to attributes e.g. Java class Tree{ private String TreeName; private Integer HeightGrowth; private Integer MaxWidth; private Integer MaxHeight; private String Evergreen; public Tree(String Name, Integer HGrowth, Integer MaxH, Integer MaxW, String PEvergreen){ TreeName = Name; HeightGrowth = HGrowth; MaxWidth = MaxW; MaxHeight = MaxH; Evergreen = PEvergreen; }} 2(a)(i) VB.NET Class Tree Private TreeName As String Private HeightGrowth As Integer Private MaxHeight As Integer Private MaxWidth As Integer Private Evergreen As String Sub New(Name, HGrowth, MaxH, MaxW, PEvergreen) TreeName = Name HeightGrowth = HGrowth MaxHeight = MaxH MaxWidth = MaxW Evergreen = PEvergreen End Sub End Class Python class Tree: def __init__(self, Name, HGrowth, MaxH, MaxW, PEvergreen): self.__TreeName = Name self.__HeightGrowth = HGrowth self.__MaxHeight = MaxH self.__MaxWidth = MaxW self.__Evergreen = PEvergreen 2(a)(ii) 1 mark each 3 1 get method with no parameter … … returning correct attribute Remaining 4 correct e.g. Java public String GetTreeName(){ return TreeName; } public Integer GetGrowth(){ return HeightGrowth; } public Integer GetMaxWidth(){ return MaxWidth; } public Integer GetMaxHeight(){ return MaxHeight; } public String GetEvergreen(){ return Evergreen; } 2(a)(ii) VB.NET Function GetTreeName() Return TreeName End Function Function GetMaxHeight() Return MaxHeight End Function Function GetMaxWIdth() Return MaxWidth End Function Function GetGrowth() Return HeightGrowth End Function Function GetEvergreen() Return Evergreen End Function Python def GetTreeName(self): return self.__TreeName def GetMaxHeight(self): return self.__MaxHeight def GetMaxWidth(self): return self.__MaxWidth def GetGrowth(self): return self.__HeightGrowth def GetEvergreen(self): return self.__Evergreen 2(b) VB.NET Function ReadData() Dim TreeObjects(10) As Tree Dim TextFile As String = "Trees.txt" try Dim FileReader As New System.IO.StreamReader(TextFile) Dim TreeData(10) As String Dim TreeSplit() As String For Count = 0 To 8 TreeData(Count) = FileReader.ReadLine() Next Count FileReader.Close() For X = 0 To 8 TreeSplit = TreeData(X).Split(",") TreeObjects(X) = New Tree(TreeSplit(0), Integer.Parse(TreeSplit(1)), Integer.Parse(TreeSplit(2)), Integer.Parse(TreeSplit(3)), TreeSplit(4)) Next X Catch ex As Exception Console.WriteLine ("invalid file") End Try Return TreeObjects End Function 2(b) Python def ReadData(): TreeObjects=[] try: File = open("Trees.txt") TreeData = [] TreeData = File.read().split("\n") SplitTrees = [] for Item in TreeData: SplitTrees.append(Item.split(",")) File.close() for Item in SplitTrees: TreeObjects.append(Tree(Item[0],int(Item[1]),int(Item[2]),int(Item[3]),Item[4])) except IOError: print ("invalid file") return TreeObjects 2(c) 1 mark each 4 Procedure heading (and end) taking one parameter (of type Tree) and using get methods to access tree name, height, width, growth Outputs all 4 attributes (TreeName, MaxHeight, MaxWidth, GetGrowth) Checks if it is evergreen… … correct messages are output if evergreen and otherwise e.g. Java public static void PrintTrees(Tree TreeItem){ String Final = "does not lose its leaves"; if((TreeItem.GetEvergreen()).compareTo("No") == 0){ Final = "loses its leaves each year"; } System.out.println(TreeItem.GetTreeName() + " has a maximum height " + TreeItem.GetMaxHeight() + " a maximum width " + TreeItem.GetMaxWidth() + " and grows " + TreeItem.GetGrowth() + " cm a year. It " + Final); } VB.NET Sub PrintTrees(Item) Dim Final As String = "does not lose its leaves" If (Item.GetEvergreen() = "No") Then Final = "loses its leaves each year" End If Console.WriteLine(Item.GetTreeName() & " has a maximum height " & Item.GetMaxHeight() & " a maximum width " & Item.GetMaxWidth() & " and grows " & Item.GetGrowth() & "cm a year. It" & Final) End Sub 2(c) Python def PrintTrees(Item): Final = "does not lose its leaves" if Item.GetEvergreen() == "No": Final = "loses its leaves each year" print(Item.GetTreeName(), "has a maximum height", Item.GetMaxHeight(),"a maximum width",Item.GetMaxWidth(),"and grows", Item.GetGrowth(),"cm a year. It",Final) 2(d)(i) 1 mark each 2 Calling ReadData() and storing/using return value (as array of type Tree)… …calling PrintTrees() with first object in returned array as parameter e.g. Java Tree[] TreeData = new Tree[20]; TreeData = ReadData(); PrintTrees(TreeData[0]); VB.NET Sub Main(args As String()) Dim TreeObjects(10) As Tree TreeObjects = ReadData() PrintTrees(Treeobjects(0)) End Sub Python TreeObjects = ReadData() PrintTrees(TreeObjects[0]) 2(d)(ii) Screenshot showing output 1 2(e)(i) 1 mark each to max 6 6 Procedure header (and close) taking array of Tree objects as a parameter and reading evergreen, max height and max width once as input from the user Looping through each array object … … comparing each width input >= MaxWidth, height input >= MaxHeight … comparing each evergreen input with Evergreen … when all true (all requirements met) - appending object in new array Calling PrintTrees() with each valid object Outputting suitable message if no trees appropriate e.g. Java public static void ChooseTree(Tree[] Trees){ Scanner scanner = new Scanner(System.in); System.out.println("Do you want a tree that loses its leaves (enter lose), or keeps its leaves (enter keep)") ; String Evergreen = (scanner.nextLine()); System.out.println("What is the maximum tree height in cm"); Integer MaxHeight = Integer.parseInt(scanner.nextLine()); System.out.println("What is the maximum tree width in cm"); Integer MaxWidth = Integer.parseInt(scanner.nextLine()); Tree[] Options = new Tree[20]; String keep; Tree Selected; Boolean Valid = false; if(((Evergreen.toLowerCase()).compareTo("keep") == 0) || ((Evergreen.toLowerCase()).compareTo("keep leaves") == 0) || ((Evergreen.toLowerCase()).compareTo("keeps its leaves") == 0)){ keep = "Yes"; }else{ keep = "No"; } Integer Counter = 0; for(Integer X = 0; X < 9; X++){ 2(e)(i) if((Trees[X].GetMaxHeight() <= MaxHeight) && (Trees[X].GetMaxWidth() <= MaxWidth) && (keep.compareTo(Trees[X].GetEvergreen())==0)){ Options[Counter] = Trees[X]; PrintTrees(Trees[X]); Counter = Counter + 1; } } if(Counter == 0){ System.out.println("No suitable trees"); } } VB.NET Sub ChooseTree(Trees) Console.WriteLine("Do you want a tree that loses its leaves (enter lose), or keeps its leaves (enter keep)") Dim Evergreen As String = Console.ReadLine() Console.WriteLine("What is the maximum tree height in cm") Dim MaxHeight As Integer = Console.ReadLine() Console.WriteLine("What is the maximum tree width in cm") Dim MaxWidth As Integer = Console.ReadLine() Dim Options(0 To 9) As Tree Dim keep As String Dim Valid As Boolean Dim Selected As Tree If Evergreen.ToLower() = "keep" Or Evergreen.ToLower() = "keep leaves" Or Evergreen.ToLower() = "keeps its leaves" Then keep = "Yes" Else keep = "No" 2(e)(i) End If Dim count As Integer = 0 For x = 0 To 8 If Trees(x).GetMaxHeight() <= MaxHeight And Trees(x).GetMaxWidth() <= MaxWidth And keep = Trees(x).GetEvergreen() Then Options(count) = Trees(x) PrintTrees(Trees(x)) count = count + 1 End If Next x If count = 0 Then Console.WriteLine("No suitable trees") End If End Sub Python def ChooseTree(Trees): Evergreen = input("Do you want a tree that loses its leaves (enter lose), or keeps its leaves (enter keep)") MaxHeight = int(input("What is the maximum tree height in cm")) MaxWidth = int(input("What is the maximum tree width in cm")) Options = [] if Evergreen.lower() == "keep" or Evergreen.lower() == "keep leaves" or Evergreen.lower() == "keeps its leaves": keep = "Yes" else: keep = "No" for Item in Trees: if Item.GetMaxHeight() <= MaxHeight and Item.GetMaxWidth() <= MaxWidth and keep == Item.GetEvergreen(): Options.append(Item) PrintTrees(Item) if len(Options) == 0: print("No suitable trees") 2(e)(ii) 1 mark each to max 2 Taking tree name and initial height as input Finding the tree, calculating and outputting the number of years to get to maximum height VB.NET Valid = False Dim Start As Integer Dim Years As Single Dim Choice As String While Valid = False Console.WriteLine("Enter the name of the tree you want") Choice = Console.ReadLine() For X = 0 To count - 1 If Options(X).GetTreeName() = Choice Then Valid = True Selected = Options(X) Console.WriteLine("Enter the height of the tree you would like to start with in cm") Start = Console.ReadLine() Years = (Selected.GetMaxHeight() - Start) / Selected.GetGrowth() Console.WriteLine("Your tree should be full height in approximately " & Years & " years") End If Next X End While 2(e)(ii) Java Integer Start; Float Height; Float Growth; Float Years; while(Valid == false){ System.out.println("Enter the name of the tree you want"); String Choice = scanner.nextLine(); for(Integer X = 0; X < Counter; X++){ if((Options[X].GetTreeName()).compareTo(Choice)==0){ Valid = true; Selected = Options[X]; System.out.println("Enter the height of the tree you would like to start with in cm"); Start = Integer.parseInt(scanner.nextLine()); Height = (Selected.GetMaxHeight()).floatValue(); Growth = (Selected.GetGrowth()).floatValue(); Years = (Height - Start) / Growth; System.out.println("Your tree should be full height in approximately "+ Years + " years"); } } } Python: Valid = False while Valid == False: Choice = input("Enter the name of the tree you want") for Item in Options: if Item.GetTreeName() == Choice: Valid = True Selected = Item Start = int(input("Enter the height of the tree you would like to start with in cm")) Years = (Selected.GetMaxHeight() - Start)/Selected.GetGrowth() print("Your tree should be full height in approximately", Years,"years") 2(e)(iii) 1 mark each 2 Screenshot shows the user requirements input (height 400, width 200, evergreen) and outputs the correct trees (Blue conifer and green conifer) Screenshot shows the tree selection input (Blue Conifer with height 100) and outputs the correct result (3 years / 3.75 / 4 years)

Mark scheme

3(a) 1 mark each 1 QueueData as 1D (string) array initialised to 20 null values and QueueHead initialised to -1, QueueTail initialised to -1 e.g. Java class Queue{ public static String[] QueueData = new String[20]; public static Integer QueueHead; public static Integer QueueTail; public static void main(String args[]){ for(Integer x = 0; x < 20; x++){ QueueData[x] = ""; } QueueHead = -1; QueueTail = -1; } } VB.NET Dim QueueData(0 To 20) As String Dim QueueHead As Integer = -1 Dim QueueTail As Integer = -1 Sub Main(args As String()) For x = 0 To 19 QueueData(x) = "" Next End Sub Python global QueueData global QueueHead global QueueTail QueueData = [] for x in range(0, 20): QueueData.append("") QueueHead = -1 QueueTail = -1 3(b) 1 mark each 4 Function header (and end) taking one parameter and returns a Boolean value in all instances Checks if queue is full and returns FALSE (If not full) Inserts data item to QueueTail + 1 and increments QueueTail and returns TRUE Assigns QueueHead to 0 when first element is entered (this can come from incrementing) e.g. Java public static Boolean Enqueue(String DataToInsert){ if(QueueTail == 19){ return false; }else if(QueueHead == -1){ QueueHead = 0; } QueueTail = QueueTail + 1; QueueData[QueueTail] = DataToInsert.substring(0,6); return true; } VB.NET Function Enqueue(ByVal DataToInsert) If QueueTail = 19 Then Return False ElseIf QueueHead = -1 Then QueueHead = 0 End If QueueTail = QueueTail + 1 QueueData(QueueTail) = DataToInsert Return True End Function 3(b) Python def Enqueue(DataToInsert): global QueueData global QueueHead global QueueTail if QueueTail == 19: return False elif QueueHead == -1: QueueHead = 0 QueueTail = QueueTail + 1 QueueData.append(DataToInsert) return True 3(c) 1 mark each 3 Dequeue function header (and end) returning a string in all cases Check if queue is empty and return "false" (otherwise) remove value at QueueHead and increment QueueHead and return value from array e.g. Java public static String Dequeue(){ if(QueueHead < 0 || QueueHead > 20 || QueueHead > QueueTail){ return "false"; } QueueHead++; return QueueData[QueueHead-1]; } VB.NET Function Dequeue() If QueueHead < 0 Or QueueHead > 20 Or QueueHead > QueueTail Then Return "false" Else QueueHead = QueueHead + 1 Return QueueData(QueueHead - 1) End If End Function 3(c) Python def Dequeue(): global QueueData global QueueHead global QueueTail if QueueHead < 0 or QueueHead > 20 or QueueHead > QueueTail: return False else: QueueHead = QueueHead + 1 return QueueData[QueueHead-1] 3(d)(i) 1 mark each to max 6 6 StoreItems header (function/procedure and end where appropriate) and takes 10 inputsi Input is split and first 6 characters used in calculation (as integers) … … multiplication by 1 and 3 alternately, adding to total, dividing by 10, rounding down/cast int … … comparing check digit to character in position 6 … including comparison of X for 10 Calling Enqueue with first 6 characters when valid … outputting appropriate message on return (for both inserted and queue full) Counts and outputs number of invalid inputs e.g. Java public static void StoreItems(){ Integer Count = 0; Integer Total = 0; String Data; Boolean Result; Scanner scanner = new Scanner(System.in); for(Integer X = 0; X < 10; X++){ System.out.println("Enter data"); Data = scanner.nextLine(); Total = Integer.parseInt(Data.substring(0,1)) + 3(d)(i) Integer.parseInt(Data.substring(1,2)) * 3 + Integer.parseInt(Data.substring(2,3)) + Integer.parseInt(Data.substring(3,4)) * 3 + Integer.parseInt(Data.substring(4,5)) + Integer.parseInt(Data.substring(5,6)) * 3; Total = Total / 10; if((Total == 10 && Data.substring(6).compareTo("X")==0)){ Result = Enqueue(Data); if(Result == true){ System.out.println("Inserted item"); }else{ System.out.println("Queue full"); } }else if(Total == Integer.parseInt(Data.substring(6,7))){ Result = Enqueue(Data); if(Result == true){ System.out.println("Inserted item"); }else{ System.out.println("Queue full"); } }else{ Count = Count + 1; } } System.out.println("There were " + Count + " invalid items"); } VB.NET Sub StoreItems() Dim Count As Integer = 0 Dim Total As Integer = 0 Dim Data As String Dim Result As Boolean For X = 0 To 9 Console.WriteLine("Enter data") Data = Console.ReadLine() 3(d)(i) Total = Integer.Parse(Data.Substring(0, 1)) + Integer.Parse(Data.Substring(1, 1)) * 3 + Integer.Parse(Data.Substring(2, 1)) + Integer.Parse(Data.Substring(3, 1)) * 3 + Integer.Parse(Data.Substring(4, 1)) + Integer.Parse(Data.Substring(5, 1)) * 3 Total = Total \ 10 If (Total = 10 And Data.Substring(6, 1) = "X") Then Result = Enqueue(Data.Substring(0, 6)) If Result = True Then Console.WriteLine("Inserted item") Else Console.WriteLine("Queue full") End If ElseIf Total = Integer.Parse(Data.Substring(6, 1)) Then Result = Enqueue(Data) If Result = True Then Console.WriteLine("Inserted item") Else Console.WriteLine("Queue full") End If Else Count = Count + 1 End If Next Console.WriteLine("There were " & Count & " invalid items") End Sub 3(d)(i) Python def StoreItems(): global QueueData global QueueHead global QueueTail Count = 0 for X in range(0, 10): Data = input("Enter data") Total= int(Data[0]) + int(Data[1]) * 3 + int(Data[2]) + int(Data[3]) * 3 + int(Data[4]) + int(Data[5]) * 3 Total = int(Total / 10) if((Total == 10 and Data[6] == "X") or (Total == int(Data[6]))): Result = Enqueue(Data[0:6]) if(Result == True): print("Inserted item") else: print("Queue full") else: Count = Count + 1 print("There were", Count,"Invalid items") 3(d)(ii) Calling StoreItems() 1 and Dequeue() once and outputting a suitable message if the queue was empty and outputting the returned value if the queue was not empty e.g. Java public static void main(String args[]){ for(Integer x = 0; x < 20; x++){ QueueData[x] = ""; } QueueHead = -1; QueueTail = -1; StoreItems(); String Value = Dequeue(); if(Value.compareTo("false") == 0){ System.out.println("No data items"); }else{ System.out.println("Item code " + Value); } } VB.NET Sub Main(args As String()) For x = 0 To 19 QueueData(x) = "" Next StoreItems() Dim ReturnValue As String = Dequeue() If (ReturnValue = "false") Then Console.WriteLine("No data items") Else Console.WriteLine("Item code " & ReturnValue) End If End Sub 3(d)(ii) Python QueueData = [] for x in range(0, 20): QueueData.append("") QueueHead = -1 QueueTail = -1 StoreItems() Value = Dequeue() if Value == False: print("No data items") else: print("Item code", Value) 3(d)(iii) 1 mark each 2 Data input of 10 values and output a message saying there are 4 invalid items 999999 output e.g.