CODEWITHSUNDEEP
c#arrays
Matt
Matt

Reputation: 75

Which elements of the two arrays do not match

I have a program that grades multiple choice answers from a text file against the correct answers defined in another array. It is all working properly but I want to add the ability to show which question numbers are incorrect so the user knows where they went wrong. Below is the code I have minus any attempts to create this functionality.

using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Drawing;
using System.IO;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using System.Windows.Forms;

namespace Assignment1_Part_2b
{
    public partial class Form1 : Form
    {
        public Form1()
        {
            InitializeComponent();
        }

        private void exitBtn_Click(object sender, EventArgs e)
        {
            this.Close();
        }

        private void btnCalculate_Click(object sender, EventArgs e)
        {
            string[] answers = { "B", "D", "A", "A", "C", "A", "B", "A", "C", "D", 
                                   "B", "C", "D", "A", "D", "C", "C", "B", "D", "A" };

            string[] studentAnswers = new string[20];
            studentAnswers = File.ReadAllLines("StudentAnswers.txt");
            int correct = 0;
            int incorrect = 0;
            int totalMark;


            for (int i = 0; i < answers.Length; i++)
            {
                if (answers[i] == studentAnswers[i])
                {
                    correct = (correct + 1);
                }
                else
                {
                    incorrect = (incorrect++);
                }
                totalMark = (correct - incorrect);
                wrongAnswerLabel.Text = incorrect.ToString();
                correctLabel.Text = correct.ToString();

                if (totalMark > 14)
                {
                    resultTextBox.Text = "Pass";
                }
                else
                {
                    resultTextBox.Text = "Fail";
                }


            }      
        }

        private void btnClear_Click(object sender, EventArgs e)
        {
            ClearAll();
        }
        private void ClearAll()
        {
            resultTextBox.Text = "";
            incorrectLabel.Text = "";
        }

    }
}

I am stuck for ideas on how I would approach this so any help would be appreciated.

Thanks guys.

Upvotes: 1

Views: 89

Answers (3)

Nicholas Carey
Nicholas Carey

Reputation: 74307

You can use a Linq one-liner:

public int[] WrongAnswers( char[] reference , char[] answer )
{
  if ( reference.Length != answer.Length ) throw new ArgumentOutOfRangeException();
  int[] wrongAnswers = Enumerable
                       .Range(0,reference.Length)
                       .Select( i => new Tuple<int,bool>( i , reference[i]==answer[i] ) )
                       .Where( x => !x.Item2)
                       .Select( x => x.Item1 )
                       .ToArray()
                       ;
  return wrongAnswers ;
}

You can do something like this:

public int[] WrongAnswers( char[] reference , char[] answer )
{
  if ( reference.Length != answer.Length ) throw new ArgumentOutOfRangeException();
  List<int> wrongAnswers = new List<int>() ;
  for ( int i = 0 ; i < reference.Length ; +=i )
  {
    if ( reference[i] != answer[i] ) wrongAnswers.Add(i) ;
  }
  return wrongAnswers.ToArray() ;
}

Upvotes: 2

Selman Gen&#231;
Selman Gen&#231;

Reputation: 101701

Declare another list to store indices of wrong answers:

var wrongAnswers = new List<int>();

Then if answer is incorrect add it's index to the list:

else
{
    incorrect = (incorrect++);
    wrongAnswers.Add(i + 1); 
}

Btw instead of this incorrect = (incorrect++); you could just use incorrect++;

Also I think you might want to move these lines outside of your loop:

totalMark = (correct - incorrect);
wrongAnswerLabel.Text = incorrect.ToString();
correctLabel.Text = correct.ToString();

if (totalMark > 14)
{
    resultTextBox.Text = "Pass";
}
else
{
     resultTextBox.Text = "Fail";
}

In order to display wrong answer numbers you could use String.Join and concatenate numbers into single string and display it like this:

string text = string.Join(" ", wrongAnswers);

wrongAnswersLabel.Text = "Wrong answers: " + text;

Upvotes: 3

aw04
aw04

Reputation: 11187

You can define an array or a list outside of your loop and add the question number to it when incorrect. You'll end up with the list of incorrect questions.

Upvotes: 0

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