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Using Modulo instead of two loops

I'm new at programming in general and learning C# right now.
I just wrote a little programm where I have to step through an int[] in a specific pattern. The pattern is as follows:
Start at the last entry of the array (int i)
form the sum of i and (if avaible) the three entrys above (e.g. i += i-1 ... i += i-3)
Change i to i -= 4 (if avaible)
Repeat from step 2 until i = 0;
Therefore i wrote the following loop:
for (int i = intArray.Length - 1; i >= 0; i -= 4)
{
for (int a = 1; a <= 3; a++)
{
if (i - a >= 0)
{
intArray[i] += intArray[i - a];
intArray[i - a] = 0;
}
}
}
Now my new assignment is to change my code to only use 1 loop with the help of modulo-operations. I do understand what modulo does, but i can't figure out how to use it to get rid of the second loop.
Maybe somebody explain it to me? Thank you very much in advance.

While iterating over the array, the idea would be to use the modulo 4 operation to calculate the next index to which you will add the current value.
This should work with any array lengths:
for (int i = 0; i < intArray.Length; i++){
// we check how far away we are from next index which stores the sum
var offset = (intArray.Length - 1 - i) % 4;
if (offset == 0) continue;
intArray[i+offset] += intArray[i];
intArray[i] = 0;
}

iterating the array reversely makes it a bit more complicated, but what you wanted to get rid of inner loop with modulo is probably this:
var intArray = Enumerable.Range(1, 15).ToArray();
for (int i = 1; i < intArray.Length - 1; i ++)
{
intArray[i - (i % 4)] += intArray[i];
intArray[i] = 0;
}

How do I print just a final sum in this problem?

I am a beginner, trying to solve Project Euler problem 1:
"If we list all the natural numbers below 10 that are multiples of 3 or 5, we get 3, 5, 6 and 9. The sum of these multiples is 23.
Find the sum of all the multiples of 3 or 5 below 1000.", but, you probably know this problem.
So I get a correct answer but my program lists all sums up to a final sum. But how do I manage to just print final sum?
int x = 0;
for (int i = 1; i < 1000; i ++)
{
if (i % 3 == 0 || i % 5 == 0)
{
Console.WriteLine(x += i);

You have a Console.WriteLine inside a loop, so every time the if is true, a print out to the console will occur. Move the Console.WriteLine so it is outside of the loop
I think you would have quite quickly discovered this problem if you had used the debugger to step through the code line by line. Do you know how to use the debugger? If not, drop a comment and I'll write some introductory lines

You should keep console.WriteLine() outside of 'for' loop,
Your code should go look like this-
int x=0;
for (int i = 1; i < 1000; i ++){
if (i%3==0 || i%5==0){
x+=i;
}}
console.WriteLine(x);

good start bro, you can just make the Console.WriteLine(x) after the for loop

You don't need to write every time you add i to x. You can just add it and then print after you ran the for loop.
int x = 0;
for (int i = 0; i < 1000; i++)
{
if (i % 3 == 0 || i % 5 == 0)
{
x += i;
}
}
Console.WriteLine(x);

If you want to print only the final result, move the Console.WriteLine command out of the iteration and place it after it. This way it will execute only once.
int x = 0;
for (int i = 1; i < 1000; i ++)
{
if (i % 3 == 0 || i % 5 == 0)
{
x += i;
}
}
Console.WriteLine(x);

How to print below Star pattern

I can't get this answer:
*****
****
***
**
*
Multidimensional arrays, nested (do..while, while, for)
char[,] stars = new char[5, 3];
for (int i = 0; i < 5; i++)
{
for(int x=0;x<3;x++)
{
stars[i,x]=char.Parse("*");
Console.Write(stars[i, x]);
I want to get 5 "*" stars then 4 in a new Line then 3 in a new Line then 1 in a new Line

Here you need to understand pattern behind *.
star pattern in your program is,
0st Line : 5 starts //Considering starting index is 0
1st Line : 4 starts // starts = n starts - Line no. where n = 5
2nd Line : 3 starts
3rd Line : 2 starts
4th Line : 1 starts
i.e.
Number of stars in single line = n starts - Line number //
where n = 5
So your code will look like,
int n = 5;
for (int i = 0; i < n; i++)
{
for (int j = 0; j < n - i; j++)
{ //^^^^^ n - i is key behind this * pattern
Console.Write("*");
}
Console.WriteLine();
}

As this is not about array indexing or address calculation but actual countable objects (stars), I feel that 1-based indexes make more sense here.
Also, the number of stars should be decreasing, so counting backwards makes more sense as well:
for (int numStars = 5; numStars >= 1; --numStars)
{
for (int star = 1; star <= numStars; ++star)
Console.Write("*");
Console.WriteLine();
}

c# Loops with stars and spaces

I am currently breaking my head over this simple assignment for loops that I have to do.
Basically what I want to achieve is:
1) User gives imput how long the star pyramid should be
2) Make a pyramid with a for loop.
It needs to look something like this:
(If it needs to be 5 stories high; first row is 5 spaces 1 star; second row 4 spaces 2 stars and so on.
*
**
***
****
(Hard to format but you get my intention.)
I currently have this
public void Pyramid()
{
Console.WriteLine("Give the hight of the pyramid");
_aantal = Convert.ToInt32(Console.ReadLine());
for (int i = 1; i <= _aantal; i++) // loop for hight
{
for (int d = _aantal; d > 0; d--) // loop for spaces
{
Console.Write(_spatie);
}
for (int e = 0; e < i; e++) // loop for stars
{
Console.Write(_ster);
}
Console.WriteLine();
}
}
The output is always the inserted number amount of spaces and it is not decremented correctly.
Although if I debug it it counts down correctly.
Thank you for responding.

You could use the constructor of the string class to create the repetition for you, and then print both values at once, then you don't need the extra for loops
static void Main(string[] args)
{
int rowHeight = 5;
for (int row = 1; row <= rowHeight; row++)
{
string spaces = new string(' ', rowHeight - row);
string stars = new string('*', row);
Console.WriteLine("{0}{1}", spaces, stars);
}
Console.ReadLine();
}
UPDATE
for the semantics, i will then also show it with 2 for loops
static void Main(string[] args)
{
int rowHeight = 5;
for (int row = 1; row <= rowHeight; row++)
{
int totalSpaces = rowHeight - row;
for (int j = 0; j < totalSpaces; j++)
{
Console.Write(" ");
}
for (int j = 0; j < row; j++)
{
Console.Write("*");
}
Console.WriteLine();
}
Console.ReadLine();
}

well, your problem is
for (int d = _aantal; d > 0; d--) // loop for spaces
you really want
for (int d = _aantal - i ; d > 0; d--) // loop for spaces
but it really just mirrors what you currently have, and still doesn't create the pyramid look you seem to want.
I think the closest you'll get in a console app is by subtracting a space every other row:
for (int d = _aantal-i; d > 0; d-=2) // loop for spaces
which will give output:
Give the hight of the pyramid:
10
*
**
***
****
*****
******
*******
********
*********
**********

Got it !
static void Main(string[] args)
{
Console.WriteLine("Give the hight of the pyramid");
string _spatie = " ";
string _ster = "*";
int _aantal = Convert.ToInt32(Console.ReadLine());
for (int i = 1; i <= _aantal; i++) // loop for height
{
for (int d = i; d < _aantal; d++) // loop for spaces
{
Console.Write(_spatie);
}
for (int e = 1; e <= i; e++) // loop for stars
{
Console.Write(_ster);
}
Console.WriteLine();
}
Console.ReadKey();
}
Check this out..!! You were missing out the iterator 'i' of the height loop inside the spaces loop.
You will get the triangle :-
*
**
***
****
You will need odd number of stars always for a symmetrical pyramid.

I know you wanted to do this as a console app but if you adapt this code it should work fine
Replace textbox1/2 with Consle.Readline/Write
int pyramidstories = int.Parse(TextBox2.Text);
int I = 1;
while (I <= pyramidstories)
{
for (int spacecount = 0; spacecount < (pyramidstories - I); spacecount++)
{
TextBox1.Text += " ";
}
for (int starcount = 1; starcount < I + 1; starcount++)
{
TextBox1.Text += "*";
}
TextBox1.Text += Environment.NewLine;
I++;
}
As your question states you need:
4 spaces 1 star
3 spaces 2 stars
2 spaces 3 stars
etc..
so your pyramid should look something like
*
**
***
****
*****
The code sample above displays a pyramid as illustrated above

To get a pyramid (with proper spacing) like this:
You can use:
static void Main(string[] args)
{
// The length of the pyramid
int lengte = 18;
// Loop through the length as given by the user
for (int i = 0; i <= lengte; i++)
{
// If its an even number (we don't want 1-2-3.. but 1-3-5.. stars)
if (i % 2 == 0)
{
// Calculate the length of the spaces we need to set
int spatieLengte = (lengte / 2) - (i / 2);
// Display spaces
for (int spaties = 0; spaties <= spatieLengte; spaties++)
{
Console.Write(" ");
}
// Display stars
for (int sterren = 0; sterren <= i; sterren++)
{
Console.Write("*");
}
// Newline
Console.WriteLine();
}
}
Console.ReadLine();
}
Obviously the if block and spaceLengte variable aren't really needed. But I thought it would make it somewhat easier for OP to read.
Good luck / Succes ermee ;)

c# - WriteLine overlap

Is it possible to write a loop that will write to the console with overlapping text?
Desired output:
Notice how the lines overlap. I was using '|' vertically and '-' horizontally.
The vertical line is the 4th column and the horizontal line is the 3rd row.
I know this is way off:
for (int i = 1; i <= 4; i++)
{
Console.Write(" | ");
for (int x = 1; x <= 6; x++)
{
Console.Write(" - ");
}
}

Try Extended ASCII Codes. These might help you draw pretty pseudographics:
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