C#•3y ago

✅ array.sort help

I got the stuff down, but I don’t think it’s right

112 Replies

JulesOP•3y ago

So I am stuck with array.sort, I need to sort the array from a text file and then find the median. But I don't think I'm doing the sorting correct...

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using System.IO;

namespace assignment5_2_
{
    class Program
    {
        static void Main(string[] args)
        {
            const int SIZE = 43;
            int[] numbers = new int[SIZE];

            int index = 0;
            int total = 0;
            //Console.WriteLine("Hello");

            StreamReader inputFile;
            inputFile = File.OpenText("Scores.txt");

            while (index < numbers.Length && !inputFile.EndOfStream)
            {
                numbers[index] = int.Parse(inputFile.ReadLine());
                //Console.WriteLine(numbers[index]);
                index++;
            }
            inputFile.Close();
            int highest = numbers[0];
            int lowest = numbers[0];

            for (int i = 0; i < numbers.Length; i++)
            {
                total += numbers[i];
            }
                Console.WriteLine(total/numbers.Length);
            for (int h = 1; h < numbers.Length; h++)
            {
                if (numbers[h] > highest)
                {
                    highest = numbers[h];
                }
            }
            Console.WriteLine(highest);
            for (int l = 1; l < numbers.Length; l++)
            {
                if (numbers[l] < lowest)
                {
                    lowest = numbers[l];
                }
            }
            Array.Sort(numbers);

            Console.WriteLine(lowest);
            Console.WriteLine(total);
            Console.ReadLine();
        }
    }
}

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using System.IO;

namespace assignment5_2_
{
    class Program
    {
        static void Main(string[] args)
        {
            const int SIZE = 43;
            int[] numbers = new int[SIZE];

            int index = 0;
            int total = 0;
            //Console.WriteLine("Hello");

            StreamReader inputFile;
            inputFile = File.OpenText("Scores.txt");

            while (index < numbers.Length && !inputFile.EndOfStream)
            {
                numbers[index] = int.Parse(inputFile.ReadLine());
                //Console.WriteLine(numbers[index]);
                index++;
            }
            inputFile.Close();
            int highest = numbers[0];
            int lowest = numbers[0];

            for (int i = 0; i < numbers.Length; i++)
            {
                total += numbers[i];
            }
                Console.WriteLine(total/numbers.Length);
            for (int h = 1; h < numbers.Length; h++)
            {
                if (numbers[h] > highest)
                {
                    highest = numbers[h];
                }
            }
            Console.WriteLine(highest);
            for (int l = 1; l < numbers.Length; l++)
            {
                if (numbers[l] < lowest)
                {
                    lowest = numbers[l];
                }
            }
            Array.Sort(numbers);

            Console.WriteLine(lowest);
            Console.WriteLine(total);
            Console.ReadLine();
        }
    }
}

Kouhai•3y ago

Array.Sort sorts an array, you can find the median by getting the middle value.

JulesOP•3y ago

but how would i find median with the array sorting?

Kouhai•3y ago

Let's take a simple example We have this set [1, 2, 3, 4, 5] what's the median value for that set?

JulesOP•3y ago

Kouhai•3y ago

Great, if we take this set [2, 3, 4, 5] What's the median here as well?

JulesOP•3y ago

technically, both 3 and 4? sorry kinda learning disabled

Kouhai•3y ago

You're correct, so when the set has an even number of values we take both these numbers add them together and then divide them by two! So it's (3+4)/2

JulesOP•3y ago

3.5

Kouhai•3y ago

Awesome, in your case the number of values in the set (array) is odd, right?

JulesOP•3y ago

43 so yes but how would i do a sort with a text Thonk

Kouhai•3y ago

Great, let's break done the code you've written Initialize the array

const int SIZE = 43;
int[] numbers = new int[SIZE];

const int SIZE = 43;
int[] numbers = new int[SIZE];

Read file and fill the array

StreamReader inputFile;
inputFile = File.OpenText("Scores.txt");

while (index < numbers.Length && !inputFile.EndOfStream)
{
     numbers[index] = int.Parse(inputFile.ReadLine());
     index++;
}

StreamReader inputFile;
inputFile = File.OpenText("Scores.txt");

while (index < numbers.Length && !inputFile.EndOfStream)
{
     numbers[index] = int.Parse(inputFile.ReadLine());
     index++;
}

The numbers array is most likely not sorted, we can however call Array.Sort(numbers) Which will sort the array in place!

JulesOP•3y ago

is my Array.Sort in the right place??

mtreit•3y ago

What do you think?

JulesOP•3y ago

I think it should be under int total = 0 imo

Kouhai•3y ago

But the array won't be filled yet

mtreit•3y ago

What would be in the array at that point?

JulesOP•3y ago

so would i put it in after the input file declaration?

mtreit•3y ago

Your algorithm should be: Read all of the data into the array. Sort the array. Compute the median. Where to put the sort should follow from that.

JulesOP•3y ago

alright, got it but im still confused on how to find the median ohgawsh

mtreit•3y ago

I think @Kouhai already gave a great explanation of how to do that. What part is confusing you?

JulesOP•3y ago

im also supposed to display what the median is would i just do Console.WriteLine(Array.Sort(numbers));?

mtreit•3y ago

What do you intend that to do? First, notice that Array.Sort returns void.

JulesOP•3y ago

show the median

mtreit•3y ago

So you just asked if you should do: Console.WriteLine(void);

JulesOP•3y ago

... oh

mtreit•3y ago

Remember, when you call a method you can mentally replace that call with the result that it returns.

JulesOP•3y ago

im sorry, i'm still a bit confused like im really slow

Kouhai•3y ago

as mtreit said Array.Sort returns void, that means it returns nothing it doesn't make sense to call Console.WriteLine with nothing, right?

JulesOP•3y ago

That’s right

Kouhai•3y ago

Okay great, basically Array.Sort sorts an array in place, what does in place mean? it means it mutates the array passed to it instead of returning a newly sorted array!

JulesOP•3y ago

But how would I show the result of the sorting?

Kouhai•3y ago

You only need the median right? So you don't have to show the whole array!

JulesOP•3y ago

yep! how would i show the median then?

Kouhai•3y ago

Let's ask another question first. How to show the first element in an array?

JulesOP•3y ago

uhhh i wouldnt do a console writeline, right?

Kouhai•3y ago

Console.WriteLine as the name suggests just writes something to the console (terminal) and moves the caret to a new line (i.e the next time your write something to the console it'll be on an a new line) So you can use Console.WriteLine More importantly how would you go about accessing the first element of the array?

JulesOP•3y ago

numbers[index]?

Kouhai•3y ago

what's index in this case?

JulesOP•3y ago

the 43 numbers

Kouhai•3y ago

But that means the first element is at index 43

JulesOP•3y ago

oh im really trying but i really am having trouble understanding, im sorry

Kouhai•3y ago

No worries! Let's take an example

int[] nums = new[] {4, 9, 12, 80};

int[] nums = new[] {4, 9, 12, 80};

The value 9 is at what index?

JulesOP•3y ago

Kouhai•3y ago

Close, but not quite right Array's in c# are 0 indexed, meaning the first element starts at index 0 With that info, 9 is at what element now?

JulesOP•3y ago

OHHHH 1

Kouhai•3y ago

Awesome, what about the index of the last element? What is it?

JulesOP•3y ago

Uh 3?

Kouhai•3y ago

Spot on! Let's try another array

int[] nums = new[] {1, 2, 3, 4, 5};

int[] nums = new[] {1, 2, 3, 4, 5};

Where are the first and last elements @Jules ?

JulesOP•3y ago

0, 1 and 4, 5?

Kouhai•3y ago

Yup that's exactly right! So let's say you want to get the middle element, what would be it's index?

JulesOP•3y ago

2, 3?

Kouhai•3y ago

That's indeed correct, now isn't that value the median for our set?

JulesOP•3y ago

Yes?

Kouhai•3y ago

Okay, so to get the median of an array with 5 elements, we need to access the 2nd element Let's assume we have an array of 43 elements What would be it's median's index?

JulesOP•3y ago

uhhhh lemme do the math uhhh i got 22/23

Kouhai•3y ago

How did you calculate it?

JulesOP•3y ago

i uh wrote down 0-43 and crossed like 43, 0, 42, 1

Kouhai•3y ago

You wrote the numbers from 0 to 43 and then crossed 0, 1, 42, 43?

JulesOP•3y ago

no i crossed from 43, 0, 42, and 1 i did 0 to 43 tho

Kouhai•3y ago

Okay, let's first try a smaller array first, we have an array with 9 elements Where is the median?

JulesOP•3y ago

0, 1, 2, 3, 4, 5, 6, 7, 8

Kouhai•3y ago

That means your array has 10 elements no?

JulesOP•3y ago

(4+5)/2 = 4.5? ... OH Would it be Thonk

Kouhai•3y ago

Yup the index would be 4! Now let's go back to our 43 element array What's the median's index now?

JulesOP•3y ago

would it it be 22?

Kouhai•3y ago

Why would it be 22? How is it calculated?

JulesOP•3y ago

uhhhhhh gimme min ima redo it wait is it 21?

Pobiega•3y ago

Yes. But why is it 21? Can you come up with a formula?

JulesOP•3y ago

is it this?

 for (int row = 0; row < numbers.GetLength(0); row++)
            {
                for (int col = 0; col < numbers.GetLength(1); col++)
                {
                    Console.WriteLine(numbers[row, col])
                }
            }

 for (int row = 0; row < numbers.GetLength(0); row++)
            {
                for (int col = 0; col < numbers.GetLength(1); col++)
                {
                    Console.WriteLine(numbers[row, col])
                }
            }

cause im looking over videos as well but im confused

Kouhai•3y ago

Before code or anything Mathematically how would you calculate it? let's say you have 13981 elements, it would be REALLY tedious to do it by hand and cross entries

JulesOP•3y ago

OHHH thats what youre Smadge

i dont know, i only know to cross which is kinda embarrassing\

Kouhai•3y ago

😅 Okay, if the set's element count is odd, we can easily calculate it like this [n+1]/2 where n is the count, but that assumes a set starts at index 1, which isn't true for C#, so how would you fit it with a 0 indexed array?

JulesOP•3y ago

[n+0]/2?

Kouhai•3y ago

Well, why not give it a try with 43?

JulesOP•3y ago

[n+43]/2??

Kouhai•3y ago

Give this one more read

JulesOP•3y ago

tryna figure it out im sorryu [43+0]/2? Is this right?

Kouhai•3y ago

That's indeed right, that expression could be simplified right?

JulesOP•3y ago

yeah?

Kouhai•3y ago

How would you go about simplifying it?

JulesOP•3y ago

43/2??

Kouhai•3y ago

Yes correct, not going back to your very first question How would you apply this information with your program logic to get the median of the array?

JulesOP•3y ago

You mean the code?

Kouhai•3y ago

yes!

JulesOP•3y ago

 for (int row = 0; row < numbers.GetLength(0); row++)
            {
                for (int col = 0; col < numbers.GetLength(21); col++)
                {
                    Console.WriteLine(numbers[row, col])
                }
            }

 for (int row = 0; row < numbers.GetLength(0); row++)
            {
                for (int col = 0; col < numbers.GetLength(21); col++)
                {
                    Console.WriteLine(numbers[row, col])
                }
            }

Kouhai•3y ago

I meant your original code at the start of the thread

mtreit•3y ago

Where did a multi-dimensional array suddenly come from in this discussion? 👀

JulesOP•3y ago

OHHHH Videos

mtreit•3y ago

What do you mean exactly?

JulesOP•3y ago

My instructors videos… aren’t the greatest :/ I asked her about this a few hours ago before this thread

mtreit•3y ago

Well, you just pasted code that seems to be from a completely unrelated problem to the one being discussed here.

JulesOP•3y ago

All she sent me was this video that had this code on it That’s why I’m kinda lost

mtreit•3y ago

I think I would forget what she sent you for the moment and focus on what @Kouhai has taught you. You might be overcomplicating things.

JulesOP•3y ago

Probably am overcomplicating things nekocry

really sorry I’m guessing… would it be Array.Sort(numbers[43/2]);? Or am I wrong..?

mtreit•3y ago

What is numbers[43/2] going to return? Do you know what "indexing into an array" means?

JulesOP•3y ago

It errors

mtreit•3y ago

I'm sure it does You effectively did this:

int index = numbers[21];
Array.Sort(index);

int index = numbers[21];
Array.Sort(index);

Does that make any sense? You can't sort a single integer value. Sort should only be done once on the entire array. Once the array is sorted you can compute the median index and look up the value at that index. That's what your code needs to do: Create the array Sort the array Compute the median index Fetch the value at that index Return that value (Sticking with the simpler case that there are an odd number of values in the array)

JulesOP•3y ago

Like I understand what you guys are telling me but it’s really hard for me to understand with my code ;__;

mtreit•3y ago

public int GetMedian(int[] unsortedNumbers)
{
    // Sort the array.

    // Compute the median index.

    // Fetch the value at that index in the array.

    // Return the value.
}

public int GetMedian(int[] unsortedNumbers)
{
    // Sort the array.

    // Compute the median index.

    // Fetch the value at that index in the array.

    // Return the value.
}

Translate the comments into code. If you are not sure how to do that for one of those comments, ask. I know you know how to do the first two.

JulesOP•3y ago

fetching the value, im not sure how to do that

mtreit•3y ago

You "index into" the array. Like this:

var item = someArray[index];

var item = someArray[index];

If you don't know how to index into an array I might suggest you go back through a basic C# tutorial. We usually recommend $helloworld

MODiX•3y ago

Written interactive course https://learn.microsoft.com/en-us/users/dotnet/collections/yz26f8y64n7k07 Videos https://dotnet.microsoft.com/learn/videos

MODiX•3y ago

mtreit#6470

REPL Result: Success

using System;
string[] someArray = new string[] { "A", "B", "C" };

// Fetch the second element!
int index = 1;
string secondString = someArray[index];

Console.WriteLine($"Fetched the string '{secondString}' at index {index} in the array!");

using System;
string[] someArray = new string[] { "A", "B", "C" };

// Fetch the second element!
int index = 1;
string secondString = someArray[index];

Console.WriteLine($"Fetched the string '{secondString}' at index {index} in the array!");

Console Output

Fetched the string 'B' at index 1 in the array!

Fetched the string 'B' at index 1 in the array!

Compile: 672.460ms | Execution: 43.349ms | React with ❌ to remove this embed.

JulesOP•3y ago

public int GetMedian(int[] unsortedNumbers)
{
    // Sort the array.
Array.Sort(numbers);
    // Compute the median index.
int index = numbers[43]
    // Fetch the value at that index in the array.
int index = 21;
string secondstring = numbers[index];
    // Return the value.
Console.WriteLine([index]);
}

public int GetMedian(int[] unsortedNumbers)
{
    // Sort the array.
Array.Sort(numbers);
    // Compute the median index.
int index = numbers[43]
    // Fetch the value at that index in the array.
int index = 21;
string secondstring = numbers[index];
    // Return the value.
Console.WriteLine([index]);
}

like.. this?

mtreit•3y ago

The fact that you have a variable named secondString when your code doesn't use strings at all implies you are just copy pasting code and hoping it will work. Stop doing that and think carefully about what you are doing. Use variable names that make sense for the problem you are working on. Why did you write this line of code?

int index = numbers[43]

int index = numbers[43]

You should replace your Console.WriteLine with this:

// Return the value
return median;

// Return the value
return median;

JulesOP•3y ago

i did have return

mtreit•3y ago

And then figure out how to make the rest of your code create a variable called median with the correct value.

JulesOP•3y ago

but would it not actually put it in the console like console.writeline?

mtreit•3y ago

If you want to print out the result, do that in the code that calls the GetMedian function.

var median = GetMedian(numbers);
Console.WriteLine(median);

var median = GetMedian(numbers);
Console.WriteLine(median);

JulesOP•3y ago

Accord•2y ago

Was this issue resolved? If so, run /close - otherwise I will mark this as stale and this post will be archived until there is new activity. Closed!

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✅ array.sort help