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How can I calculate numbers (for example) from 1 - 10 with the next number. (1+2+3+4+ ...) [closed]

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Does it have a shorter way than doing something like this:
int[] Summe = new int[6];
Summe[0] = 1;
Summe[1] = 2;
Summe[2] = 3;
Summe[3] = 4;
Summe[4] = 5;
Summe[5] = 6;
Console.WriteLine(Summe[0] + Summe[1] + Summe[2] + Summe[3] + Summe[4] + Summe[5]);
Console.ReadKey();

Using the Enumerable.Sum() method which computes the sum of a sequence of numeric values and Enumerable.Take() which returns a specified number of contiguous elements from the start of a sequence.
Console.WriteLine(Summe.Take(10).Sum());

OR from high school
// sum of integers from 1 to n
int SumNaturalNumbers(int n)
{
return n * (n + 1) / 2;
}
Formula for the general algebraic series starting from a and difference between terms d (Arithmetic progression and series)
sum = n / 2 * (2 * a + (n - 1) * d)

I think using a foreach loop may be helpful here, since you're dealing with an array. Also, you can define your array on one line.
int[] Summe = { 1, 2, 3, 4, 5, 6 };
int total = 0;
foreach (int number in Summe)
{
total += number;
}
Console.WriteLine(total);
Console.ReadKey();

You can simplify this process by simply putting this operation into a while loop.
int i = 0; // tell your program what 'i' should be upon first running the code
while (i < 10) // if 'i' is less than 10, run this block of code. You can change 10 to anything you want
{
Console.WriteLine("i = {0}", i);
i++; // increment
}
This will print each number individually, but you want to calculate the sum of every number, so you could do something like this:
{
public static void Main()
{
int j, sum = 0;
Console.Write("\n\n");
Console.Write("Find the sum of first 10 natural numbers:\n");
Console.Write("----------------------------------------------");
Console.Write("\n\n");
Console.Write("The first 10 natural number are :\n");
for (j = 1; j <= 10; j++)
{
sum = sum + j; // add the previous number to the current one
Console.Write("{0} ",j);
}
Console.Write("\nThe Sum is : {0}\n", sum);
}
}
The above code prints the sum of the first 10 natural numbers. I added some additional lines simply to make the program more legible. Again, you can change the number 10 to whatever number you want.

Creating array of elements c# console [closed]

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i just try to make this.
writing a program which create an array of of integer numbers and initializes each the elements with the element's index value, multiplid by five.
print the result
and my code is :..
Console.Title = " Arrays ";
Console.BackgroundColor = ConsoleColor.White;
Console.ForegroundColor = ConsoleColor.Black;
Console.Clear();
Console.WriteLine(" This Program Is About Partial Automation Array :-");
Console.WriteLine(" ====================================================");
Console.Write("\n Please Enter The Size Of Array : ");
int n = Convert.ToInt32(Console.ReadLine());
int[] arr1 = new int[n];
Console.WriteLine(" =====================================");
// Multible Process :-
for (int i = 0; i < n; i++)
{
arr1[i] = arr1[i] * 5;
}
// Displaying Process :-
Console.WriteLine(" \nThe Result Is :-");
Console.WriteLine(" ================");
for (int i = 0; i < n; i++)
{
Console.Write(" "+ arr1[i] + "\t");
}

Please change arr1[i] = arr1[i] * 5; to arr1[i] = i * 5;

use linq:
const int N = 10;
var array = Enumerable.Range(0, N)
.Select((x, i) => i * 5)
.ToArray();
foreach (var element in array) {
Console.WriteLine($"Value: {element}");
}

C# - program about while loop [duplicate]

This question already has answers here:
What is a debugger and how can it help me diagnose problems?
(2 answers)
Closed 4 years ago.
I'm a newbie to C# Programming and we're still starting on the loops. For our exercise today, we were tasked to create program using (while loop).
the question is :
Read 5 marks from the user, print the sum and "Passed" if the marks greater or equal to 50 or if among the marks there is only one mark less than 50.
if the user enters 2 marks less than 50 then the program should print STOP and end the program.
this is my try
unfortunately not complete and I can't do it
May you help me, please ?
int sum=0 , counter = 0, number=0 ;
while (counter < 5 || number < 50)
{
number = Convert.ToInt16(Console.ReadLine());
sum = sum + number;
counter++;
}
Console.WriteLine(sum + "\nPassed");

In the while loop you need && (and) instead of || (or).
After reading a number you can check if it's less than 50 or not and you can also count these.
So after the loop you need to check the lessCounter to decide to print Passed or STOP.
int sum = 0, counter = 0, number = 0, lessCounter = 0;
while (counter < 5 && lessCounter <= 1)
{
number = Convert.ToInt16(Console.ReadLine());
sum += number;
if (number < 50)
lessCounter++;
counter++;
}
if (lessCounter <= 1)
Console.WriteLine(sum + "\nPassed");
else
Console.WriteLine(sum + "\nSTOP");

Thank you all for all your effort and a time, special thanks to Mr.Szkup.
I was able to do it this way:
int number = 0, sum = 0, count = 0;
while (number < 5)
{
Console.Write("Input Number {0} : " , (number + 1));
int mark = Convert.ToInt16(Console.ReadLine());
if (mark < 50)
{
count++;
}
if (count == 2)
{
Console.WriteLine("\nStop\n");
break;
}
sum += mark;
number++;
}
if (count <= 1)
{
Console.WriteLine("\nsum = {0}\nPassed\n",sum);
}

Why is my for loop stopping before last index? [closed]

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I want to read 20 items but only 19 are read through console. Any idea why ?
What I'd like my code to do is :
1st : read the interger k from the standard input buffer (console)
2nd : read 20 integers into the array int x[]
static void Main(string[] args)
{
int k ;
int[] x = new int [20];
int[] y = new int [20];
int[] yval = new int[20];
int i;
Console.WriteLine("Enter k value");
k = Console.Read();
Console.WriteLine("Enter x values\n ");
for (i = 0; i <=19 ; i+=1)
{
x[i] = int.Parse(Console.ReadLine());
yval[i] = (x[i] + k) % 26;
}
}

Jon addressed the root of the problem in the comments, but I wanted to try to answer more fully. Console.Read() will only read a single character and return an integer representing the character, probably not what you want. Any characters after that are immediately read on the first pass, probably not what you expected. The issue can be illustrated by inspecting the values:
static void Main(string[] args)
{
int k;
int[] x = new int[20];
int[] y = new int[20];
int[] yval = new int[20];
int i;
Console.WriteLine("Enter k value");
k = Console.Read();
Console.WriteLine("k = {0}", k);
Console.WriteLine("Enter x values\n ");
for (i = 0; i <= 19; i += 1)
{
var input = Console.ReadLine();
x[i] = int.Parse(input);
yval[i] = (x[i] + k) % 26;
Console.WriteLine("x[{0}] = {1}", i, x[i]);
}
Console.WriteLine("Press any key...");
Console.ReadKey();
}
If you enter "12" for k, the output looks like:
Enter k value
12
k = 49
Enter x values
x[0] = 2
The first character '1' is saved to k as int value of 49 (ASCII value for '1'). The buffer still has a '2' and a newline to be read. They get read on the first pass through the loop and stored in the first element of the array.
As Jon said, you probably want k = int.Parse(Console.ReadLine()); instead.

Array ints and replace the order of number I write [closed]

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I try Start the console and after i write 5 numbers is do exsepsion what wrong in code
what the console do is after I write 5 number for example 7,4,9,5,1 ---> 1,5,9,4,7
this what I wrote
static void Main(string[] args)
{
int[] numbers = new int[5];
for (int i = 0; i < numbers.Length ; i++)
{
Console.Write("");
numbers[i] = int.Parse(Console.ReadLine());
}
for (int i = 0; i < numbers.Length / 2; i++)
{
int x = numbers[i];
numbers[i] = numbers[numbers.Length - i - 1];
numbers[numbers.Length - i - 1] = x;
}
Console.Read();

You missed two things. First - in order to swap two array items, you need to store item somewhere. Otherwise you just replace one item with other. Second - arrays have indexes from 0 to Length - 1. So you need to subtract 1 from second item index:
for (int i = 0; i < numbers.Length / 2; i++)
{
int x = numbers[i];
numbers[i] = numbers[numbers.Length - i - 1];
numbers[numbers.Length - i - 1] = x;
}