C#•14mo ago

Need help with homework

Hiya, I've been trying to solve an exercise for a bit but it's boggling me. The exercise is: Write a program that accepts a 3 digit integer (100 for exmaple) and swaps the numbers in the ones and hundreds For example: 523 -> 325 i only know up to string, and the question requires me to solve it in a way a beginner would.

109 Replies

Angius•14mo ago

How do you think it can be solved?

asianfxilureOP•14mo ago

I'm really not sure, i was thinking of using the string function but then again i have no idea how to assemble them together into one number.

Angius•14mo ago

Yes, turning the number into a string would be a good first step Then, you can use the fact that a string is really just a spicy array of chars, so you can access its elements like you would elements of an array Lastly, you can use string interpolation, for example, to put those chars back into a string, in a different order

asianfxilureOP•14mo ago

Okay, give me a minute to try working on this. Would this be possible .. ? The teacher is really vague with his teaching and he hasn't taught us interpolation (yet, i'd assume.)

int a,b;
a = Int.Parse(Console.ReadLine);
if a>99 && a<999;
string b;
string a;
b = st[2]+st[1]+st[0]

int a,b;
a = Int.Parse(Console.ReadLine);
if a>99 && a<999;
string b;
string a;
b = st[2]+st[1]+st[0]

3R1C•14mo ago

Int.Parse will throw an error if what you're inputting isn't an integer.

asianfxilureOP•14mo ago

Oops, yeah i forgot to add that the teacher requires us to have it be an integer, So it's okay.

3R1C•14mo ago

I understand that, and not to complicate things but a programmer should always try to take into account how things can fail. I might be overreaching and this might not be part of this training.

Angius•14mo ago

Also, this resembles C# but only vaguely

3R1C•14mo ago

Angius•14mo ago

Did you actually try to write and run this code?

asianfxilureOP•14mo ago

Yeah, i understand. Just that we haven't really gotten hands-down interactive yet, still on paper.

Angius•14mo ago

asianfxilureOP•14mo ago

Eh.. i have no idea how to, he's only taught us static void main and no classes or anything.

Angius•14mo ago

Well you don't need classes here Just variables, maybe a check for the value to be in range like in your pseudocode Just turn that pseudocode into actual code, try to run it, see what's wrong You will never, ever, not in a million years learn programming if you don't actually run your code

asianfxilureOP•14mo ago

What i more mean is that even with code that runs properly, i have no idea how to make it run. he's legit just taught us the basics of code, but not the basics of actually running it on a computer. I used to do python last year, i did run my codes but i genuinely have no idea how to run them now with the switch to c#.

Angius•14mo ago

What OS do you use?

asianfxilureOP•14mo ago

Windows, 11

Angius•14mo ago

Download Visual Studio 2022 then This will be the easiest way

asianfxilureOP•14mo ago

Which workload is the exact one for C#?

asianfxilureOP•14mo ago

This perhaps?

Angius•14mo ago

No, this is UWP You want the, uh, classic applications with C#?

Angius•14mo ago

This one

asianfxilureOP•14mo ago

I'm really not sure, just something to run the code. Okay, thank you.

Angius•14mo ago

Well thank you for ensuring the OP won't learn anything Spoonfeeding is worse than not answering Actually, is this code even relevant?

asianfxilureOP•14mo ago

I don't even understand it. Didn't learn any of that yet.

Angius•14mo ago

That would be another issue, yeah

3R1C•14mo ago

I'll write some comments when I have time, just a bit busy right now.

Angius•14mo ago

Yeah, don't

3R1C•14mo ago

It's okay, I can just remove it. Problem solved. Did not intend to fuck up someones day. Should've realized this is one of those "walk before you can run" ordeals.

asianfxilureOP•14mo ago

Okay, i've got it installed. Now do i create a new project, orr..?

3R1C•14mo ago

Yes

3R1C•14mo ago

or you can search for templates and find "Console App"

asianfxilureOP•14mo ago

Alright, so

int a, b;
a = Int.Parse(Console.ReadLine);
if (a > 99 && a < 999);
string b;
string a;
b = a[2] + a[1] + a[0];

int a, b;
a = Int.Parse(Console.ReadLine);
if (a > 99 && a < 999);
string b;
string a;
b = a[2] + a[1] + a[0];

fixed it up a bit, now how would i be able to run it?

Angius•14mo ago

This is almost valid C#, it should run...ish F5 runs code in VS, IIRC Or the green play arrow button

3R1C•14mo ago

Almost looks like python to me.

asianfxilureOP•14mo ago

3R1C•14mo ago

"int a,b," correct me if I'm wrong but I don't think you can declare empty nullables as non nullable and not even like this

Angius•14mo ago

Fairly self-explanatory errors

3R1C•14mo ago

Work on 1 by 1 error

asianfxilureOP•14mo ago

I really don't know, i'm confused.

Angius•14mo ago

Int does not exist Because C# is case-sensitive It has an int, but not an Int

asianfxilureOP•14mo ago

Mhm, i noticed that a bit ago, did fix it but Now it's saying Int just doesn't exist.

Angius•14mo ago

Then, you declare a and b as int variables, but later you re-declare them as string You canot redeclare variables

asianfxilureOP•14mo ago

Angius•14mo ago

Lastly, you can index a string with [], but not integers

asianfxilureOP•14mo ago

string a;
a = Console.ReadLine();
if (a.Length = 3);
{
    a = a[2] + a[1] + a[0];
}

string a;
a = Console.ReadLine();
if (a.Length = 3);
{
    a = a[2] + a[1] + a[0];
}

asianfxilureOP•14mo ago

down to two errors now... i really don't know how to continue from now.

Angius•14mo ago

== for equality

asianfxilureOP•14mo ago

Oh. Oops- My badd

3R1C•14mo ago

I like that you figured out .Length

asianfxilureOP•14mo ago

i THINK i solved it

string a;
int b;
a = Console.ReadLine();
if (a.Length == 3);
{
    b = a[2] + a[1] + a[0];
}

string a;
int b;
a = Console.ReadLine();
if (a.Length == 3);
{
    b = a[2] + a[1] + a[0];
}

3R1C•14mo ago

Angius•14mo ago

b will be a sum of digits

3R1C•14mo ago

asianfxilureOP•14mo ago

Ah, right.. it doesn't run addition though without it being an int. How.. would i solve that?

Angius•14mo ago

$interpolation

MODiX•14mo ago

String interpolation is the preferred way of building strings in C#. It is easier to read than concatenation. For example:

var foo = 1;
var bar = 2;
Console.WriteLine("foo is equal to: " + foo + " and bar is equal to: " + bar);

var foo = 1;
var bar = 2;
Console.WriteLine("foo is equal to: " + foo + " and bar is equal to: " + bar);

can be written as:

var foo = 1;
var bar = 2;
Console.WriteLine($"foo is equal to: {foo} and bar is equal to: {bar}");

var foo = 1;
var bar = 2;
Console.WriteLine($"foo is equal to: {foo} and bar is equal to: {bar}");

3R1C•14mo ago

Any way you can post your entire code?

asianfxilureOP•14mo ago

That was all of it.

3R1C•14mo ago

Here's a suggestion that might help. When you paste it in here, type '''cs at the beginning.

Angius•14mo ago

That's because char has an implicit conversion to int

asianfxilureOP•14mo ago

 string a;
int b;
a = Console.ReadLine();
if (a.Length == 3);
{
    b = a[2] + a[1] + a[0];
}

 string a;
int b;
a = Console.ReadLine();
if (a.Length == 3);
{
    b = a[2] + a[1] + a[0];
}

ive. done this a few times for python, but ive forgotton how to do it again

Angius•14mo ago

$codegif

MODiX•14mo ago

https://cdn.discordapp.com/attachments/364492811489509376/892176158312001586/code.gif

asianfxilureOP•14mo ago

ah, right the new line thank you

3R1C•14mo ago

it's okay, you don't have to include the cs but it turns it into this

 string a;
int b;
a = Console.ReadLine();
if (a.Length == 3);
{
    b = a[2] + a[1] + a[0];
}

 string a;
int b;
a = Console.ReadLine();
if (a.Length == 3);
{
    b = a[2] + a[1] + a[0];
}

Angius•14mo ago

So, again, use string interpolation So that you get a string, not an integer out of it

asianfxilureOP•14mo ago

would then for example

var ones = a[2]
var tens = a[1]
var hundreds = a[0]

var ones = a[2]
var tens = a[1]
var hundreds = a[0]

work..? ive never done interpolation, just mentioning once more.

Angius•14mo ago

You can introduce more variables here, sure It's not needed though

var x = 2 + 2;
var str = $"Value is {x}";

var x = 2 + 2;
var str = $"Value is {x}";

can just be

var str = $"Value is {2 + 2}";

var str = $"Value is {2 + 2}";

asianfxilureOP•14mo ago

does that mean you can just immediately drop for example, a[2]+a[1] into the interpolation?

Angius•14mo ago

Yeah

3R1C•14mo ago

I now realize I misread the original assignment. Did you figure this out with the interpolation?

asianfxilureOP•14mo ago

Currently trying

string a;
int b;
a = Console.ReadLine();
if (a.Length == 3);
{
    var c = ($"Value is {a[2] + a[1] + a[0]}");
}

string a;
int b;
a = Console.ReadLine();
if (a.Length == 3);
{
    var c = ($"Value is {a[2] + a[1] + a[0]}");
}

..it runs, but i'm not sure if it's correct. i'll check, one sec.

Angius•14mo ago

You're still summing the chars Each should be inserted separately into the string {a[2]}{a[1]}{a[0]}

3R1C•14mo ago

^ var c = $"{a[2]}{a[1]}{a[0]}"; The question is whether you understand why this produces the output you're looking for.

Joschi•14mo ago

A string is just a List<Char>. If you select a single letter from your string you will get back something of the type Char.

asianfxilureOP•14mo ago

Er, okay i've changed it now. But how would i print it to just check if its correct?

3R1C•14mo ago

Go head

asianfxilureOP•14mo ago

Since c isn't considered as a variable

Angius•14mo ago

Console.WriteLine() c is a variable But only exists within the scope of the if's braces $scopes

MODiX•14mo ago

scope A {
  thing a;
  scope B {
    thing b;
  }
}

scope A {
  thing a;
  scope B {
    thing b;
  }
}

thing a is available in scope A and scope B thing b is available only in scope B

asianfxilureOP•14mo ago

Ooh, i see.

FusedQyou•14mo ago

What if the number is above 999? Should that also be ignored?

3R1C•14mo ago

I'd recommend you look towards the top, in the assignment

FusedQyou•14mo ago

It says "accept a 3 digit integer" so that's vague

3R1C•14mo ago

Like I learned the hard way going into this, for him it's a "learn before you can walk" ordeal so it's not one where we take into account for user error. We assume a 3 digit input

FusedQyou•14mo ago

Says the guy that complained about Int.Parse being used

asianfxilureOP•14mo ago

string a;
a = Console.ReadLine();
if (a.Length == 3);
{
    var c = ($"{a[2]}{a[1]}{a[0]}");
    Console.WriteLine(c);
}

string a;
a = Console.ReadLine();
if (a.Length == 3);
{
    var c = ($"{a[2]}{a[1]}{a[0]}");
    Console.WriteLine(c);
}

This should be right, testing the code results in what i need.

Angius•14mo ago

Yep, LGTM

FusedQyou•14mo ago

Looks good.

3R1C•14mo ago

Did I not say I learned something?

Angius•14mo ago

You can consolidate that

string a;
a = Console.ReadLine();

string a;
a = Console.ReadLine();

into

string a = Console.ReadLine();

string a = Console.ReadLine();

too

asianfxilureOP•14mo ago

Okay, thank you all for the help! :D This was one hell of a question.. super vague too. (In terms of explanation, since the teacher barely taught us anything.)

FusedQyou•14mo ago

I suggest you look into making this even better, perhaps by making it reset itself. It gives experience and I'm sure you'd be complimented on the effort I could give you some ideas but that's obviously only if you are bothered to do that 😄

asianfxilureOP•14mo ago

At this point, no 😭 I've had enough of this question

FusedQyou•14mo ago

Understandable But the code you wrote is clear, right?

Joschi•14mo ago

Before that I suggest you change the variable names to something more expressive. Sure it's not strictly needed in short assignments like this, but it can really help solving those.

//Don't 
string a = Console.ReadLine();

// Do
string input = Console.ReadLine();

//Don't 
string a = Console.ReadLine();

// Do
string input = Console.ReadLine();

FusedQyou•14mo ago

Hold on, this code is not valid though Did you run it at all? @asianfxilure

asianfxilureOP•14mo ago

Yeah, it works.

Angius•14mo ago

Why would it not be valid?

FusedQyou•14mo ago

var c = ($"{a[2]}{a[1]}{a[0]}"); How would this work?

Angius•14mo ago

Sure, the parentheses around the string are useless But it does work

MODiX•14mo ago

Angius

REPL Result: Success

var x = ("Hello World!");
x

var x = ("Hello World!");
x

Result: string

Hello World!

Hello World!

Compile: 471.199ms | Execution: 32.474ms | React with ❌ to remove this embed.

FusedQyou•14mo ago

Oh, I'm sorry. I assumed it made a new string, but I was testing with an old verison of .NET and I think it was not supported there Carry on

Murten•14mo ago

You can also do it without a string.

MODiX•14mo ago

To compile C# code in Discord, use !eval Example:

!eval for(int i = 0; i < 4; i++) Console.WriteLine(i);

!eval for(int i = 0; i < 4; i++) Console.WriteLine(i);

Please don't try breaking the REPL service. Also, remember to do so in #bot-spam!

MODiX•14mo ago

Murten

REPL Result: Success

var x = 12345;
var y = 0;
while (x > 0)
{
    y = y * 10 + x % 10;
    x /= 10;
}
y

var x = 12345;
var y = 0;
while (x > 0)
{
    y = y * 10 + x % 10;
    x /= 10;
}
y

Result: int

Compile: 419.442ms | Execution: 40.008ms | React with ❌ to remove this embed.

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