C# and .NET Online Test

A megastore offers three types of discounts, which are represented as DiscountType enum.

Implement the GetDiscountedPrice method which should take the total weight of the shopping cart, the total price, and the discount type. It should return the final discounted price based on the discount schemes as shown in the promotional video below:

(Open full-size video in a new tab)

For example, the following code:

Console.WriteLine(GetDiscountedPrice(12, 100, DiscountType.Weight));

should print:

82.0

A class inherits a base class and it overrides a method from that base class.

Select all possible forms of the base class and its method:

A turn-based strategy game has a grid with water and land. The grid contains a true value where it's water and false where it's land.

The player controls a boat unit with a particular movement pattern. It can only move to fixed destinations from its current position as shown in the video below:

The boat can only move in a direct path through water to the possible destinations, so a destination will become unreachable if there is land in the way.

Implement the CanTravelTo function, that checks whether a destination is reachable by the boat. It should return true for destinations that are reachable according to the pattern above, and false for unreachable or out of bounds destinations which are outside the grid.

For example, consider the following code:

bool[,] gameMatrix = 
{
    {false, true,  true,  false, false, false},
    {true,  true,  true,  false, false, false},
    {true,  true,  true,  true,  true,  true},
    {false, true,  true,  false, true,  true},
    {false, true,  true,  true,  false, true},
    {false, false, false, false, false, false},
};

Console.WriteLine(CanTravelTo(gameMatrix, 3, 2, 2, 2)); // true, Valid move
Console.WriteLine(CanTravelTo(gameMatrix, 3, 2, 3, 4)); // false, Can't travel through land
Console.WriteLine(CanTravelTo(gameMatrix, 3, 2, 6, 2)); // false, Out of bounds

The following image shows valid and invalid destinations when the boat is in the position (3, 2):

Using only NUnit Framework 3's Assert.AreEqual method, write tests for the Account class that cover the following cases:

• The Deposit and Withdraw methods will not accept negative numbers.
• Account cannot overstep its overdraft limit.
• The Deposit and Withdraw methods will deposit or withdraw the correct amount, respectively.
• The Withdraw and Deposit methods return the correct results.

public class Account
{
    public double Balance { get; private set; }
    public double OverdraftLimit { get; private set; }

    public Account(double overdraftLimit)
    {
        this.OverdraftLimit = overdraftLimit > 0 ? overdraftLimit : 0;
        this.Balance = 0;
    }

    public bool Deposit(double amount)
    {
        if (amount >= 0)
        {
            this.Balance += amount;
            return true;
        }
        return false;
    }

    public bool Withdraw(double amount)
    {
        if (this.Balance - amount >= -this.OverdraftLimit && amount >= 0)
        {
            this.Balance -= amount;
            return true;
        }
        return false;
    }
}

Each of the test case methods should be in the Tester class and have the Test attribute.

A playlist is considered a repeating playlist if any of the songs contain a reference to a previous song in the playlist. Otherwise, the playlist will end with the last song which points to null.

Implement a function IsInRepeatingPlaylist that, efficiently with respect to time used, returns true if a playlist is repeating or false if it is not.

For example, the following code prints "True" as both songs point to each other.

Song first = new Song("Hello");
Song second = new Song("Eye of the tiger");
    
first.NextSong = second;
second.NextSong = first;

Console.WriteLine(first.IsInRepeatingPlaylist());

User interface contains two types of user input controls: TextInput, which accepts all characters and NumericInput, which accepts only digits.

Implement the class TextInput that contains:

• Public method void Add(char c) - adds the given character to the current value
• Public method string GetValue() - returns the current value

Implement the class NumericInput that:

• Inherits TextInput
• Overrides the Add method so that each non-numeric character is ignored

For example, the following code should output "10":

TextInput input = new NumericInput();
input.Add('1');
input.Add('a');
input.Add('0');
Console.WriteLine(input.GetValue());

Each account on a website has a set of access flags that represent a users access.

Update and extend the enum so that it contains three new access flags:

1. A Writer access flag that is made up of the Submit and Modify flags.
2. An Editor access flag that is made up of the Delete, Publish and Comment flags.
3. An Owner access that is made up of the Writer and Editor flags.

For example, the code below should print "False" as the Writer flag does not contain the Delete flag.

Console.WriteLine(Access.Writer.HasFlag(Access.Delete))

A gaming company is working on a platformer game. They need a method that will compute the character's final speed, given a map and a starting speed.

The terrain on which the game character moves forward is made from various pieces of land placed together. Implement the method CalculateFinalSpeed which takes the initial speed of the character, and an array of degrees of inclination that represent the uneven terrain.

The speed of the character will increase or decrease proportionally to the incline of the land, as shown in the image below:

The magnitude of the angle of inclination will always be < 90°. The speed change occurs only once for each piece of land. The method should immediately return 0 as the final speed if an incline reduces the speed to 0 or below 0, which makes the character lose 1 life.

For example, the below code:

Console.WriteLine(CalculateFinalSpeed(60, new int[] { 0, 30, 0, -45, 0 }));

should print:

75

Implement a function FolderNames, which accepts a string containing an XML file that specifies folder structure and returns all folder names that start with startingLetter. The XML format is given in the example below.

For example, for the letter 'u' and XML file:

<?xml version="1.0" encoding="UTF-8"?>
<folder name="c">
    <folder name="program files">
        <folder name="uninstall information" />
    </folder>
    <folder name="users" />
</folder>

the function should return "uninstall information" and "users" (in any order).

Implement function CountNumbers that accepts a sorted array of unique integers and, efficiently with respect to time used, counts the number of array elements that are less than the parameter lessThan.

For example, SortedSearch.CountNumbers(new int[] { 1, 3, 5, 7 }, 4) should return 2 because there are two array elements less than 4.

Refactor the AlertService and AlertDAO classes:

• Create a new interface, named IAlertDAO, that contains the same methods as AlertDAO.
• AlertDAO should implement the IAlertDAO interface.
• AlertService should have a public constructor that accepts IAlertDAO.
• The RaiseAlert and GetAlertTime methods should use the object passed through the constructor.

The C# method GetAppSettings returns the config settings for the app. The code below shows the Main method using it:

using System;
using System.Collections.Generic;

class Program
{
    static object GetAppSettings(bool detailed)
    {
        if (detailed)
        {
            return new Dictionary<string, string>
            {
                ["os"]      = Environment.OSVersion.ToString(),
                ["machine"] = Environment.MachineName,
                ["user"]    = Environment.UserName
            };
        }
        
        return Environment.MachineName;
    }

    static void Main()
    {
        var appSettings = GetAppSettings(true);
        Console.WriteLine(appSettings["os"]);
    }
}

The code in the Main method causes the following compile time error.

Main.cs(24,38): error CS0021: Cannot apply indexing with [] to an expression of type `object'

Explain in short why the compile error occurred in the Main method.

(An answer up to 40 words is sufficient)

You are working on a calculator application where users can input a mathematical expression such as: (3 + 5) * (2 - 4).

To correctly evaluate this expression, the application needs to validate the expression and ensure that the parentheses are balanced. The balanced parentheses are crucial for determining the order of operations and evaluating the expression correctly.

You have used an AI assistant to generate the following static method to check if the parentheses in an expression are balanced:

static bool IsBalanced(string parentheses)
{
    Stack<char> stack = new Stack<char>();
    HashSet<char> opening = new HashSet<char> { '(', '[', '{' };
    HashSet<char> closing = new HashSet<char> { ')', ']', '}' };
    Dictionary<char, char> pairs = new Dictionary<char, char>
    {
        { ')', '(' },
        { ']', '[' },
        { '}', '{' }
    };

    foreach (char c in parentheses)
    {
        if (opening.Contains(c))
        {
            stack.Push(c);
        }
        else if (closing.Contains(c))
        {
            if (stack.Count == 0 || stack.Peek() != pairs[c])
            {
                return false;
            }
            stack.Pop();
        }
    }

    return stack.Count == 0;
}

What are correct statements for the given method?

Consider the following code:

C#

public class RecyclingBin
{
    protected List<string> recyclables = new List<string>();
    
    public void Add(string recyclable)
    {
        if (recyclable.Split(' ').Length > 1 && recyclable.Split(' ')[1].Length > 3)
        {
            recyclables.Add(recyclable);
        }
    }
    
    public List<IGrouping<string, string>> SortRecyclables()
    {
        return recyclables.GroupBy(recyclable => recyclable.Split(' ').First()).ToList();
    }
}

VB.NET

Public Class RecyclingBin
    Protected recyclables As List(Of String) = New List(Of String)
    
    Public Sub Add(recyclable As String)
        If recyclable.Split(" ").Length > 1 And recyclable.Split(" ")[1].Length > 3
            recyclables.Add(recyclable)
        End If
    End Sub

    Public Function SortRecyclables()
        Return recyclables.GroupBy(Function(recyclable) recyclable.Split(" ").First()).ToList()
    End Function
End Class

Select the statements that are true if a new RecyclingBin is instantiated and the Add method is called with the following recyclable parameters: "metal pipe", "plastic toy", "metal bar", "copper wire", "plastic button", "wire", and "brass".

Which statements are true for the .NET technologies you can use to process XML data?

A company is designing the class hierarchy for various cache implementations:

public class Cache {}

public class DiskCache : Cache {}

public class MemoryCache : Cache {}

public class OptimizedDiskCache : DiskCache {}

Select all the answers that will result in a runtime exception.

Which statements are true for an int/Integer built in .NET data type?

Consider the following code:

C#

public class Crab 
{
    public virtual string PinchClaws()
    {
        return "clap clap";
    }
}

public class CoconutCrab : Crab
{
    public override string PinchClaws()
    {
        return "CLAP CLAP";
    }
}

VB.NET

Public Class Crab
    Public Overridable Function PinchClaws() As String
        Return "clap clap"
    End Function
End Class

Public Class CoconutCrab
Inherits Crab
    Public Overrides Function PinchClaws() As String
        Return "CLAP CLAP"
    End Function
End Class

Select the statements that are correct.