Can someone help me.
I need to solve these problems with c#. Verry fast!!

1. Display the first Prime "n" numbers (n=given from the keyboard)
Ex: n= 6 -> 2, 3,5,7,11,13
2. Enter a string of numbers on the keyboard until we enter "0".
After that we need to print out the Arithmetic mean of the par numbers (ex: 2) and the impair numbers (ex: 3) that we entered earlier.

Tankyou so much!!!

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Last Post by ddanbe

sounds like homework to me

why don't you give it a shot and we'll help you out

ok

1.

``````namespace ConsoleApplication2
{
class Program
{
static void Main(string[] args)
{
double n, i;
Console.WriteLine("Enter a number>");
for (i = n; i <= n; i--)

if (i >= 1)
{
if (i % 2 == 0)
Console.Write("{0}, ", i);
}
else
break;

}
}

}
``````

Edited by Nick Evan: Fixed formatting

It's not working!

ex: In don't know it!

first n, needs to be an integer

second, you need to see if its a prime number, dividing by two doesn't work (ex 9)

first n, needs to be an integer

second, you need to see if its a prime number, dividing by two doesn't work (ex 9)

can you help me with the code pls!

maybe try google, c# is prime

``````using System;
using System.Collections.Generic;
using System.Text;

namespace ConsoleApplication1
{
class Program
{
static void Main(string[] args)
{
bool current = false;
int j;

Console.WriteLine("Enter any integer");

for (int i = 2; i <= num; i++)//2 is the first prime number.
//I set i to 2 beacuse it has to print 2 firstly...
{
for (j = 2; j < i; j++)
{
if (i % j == 0)//Controls i is prime number or not...
{
current = true;
break;//breaks for not controlling anymore...
}
}
if (current == false)
Console.Write("{0} ", j);//if i is prime number, print it...
else
current = false;
}

}
}
}``````

i have to modifi it! so that
1.Display the first Prime "n" numbers (n=given from the keyboard)

would love to help, but please post the code in code tags [ not <

let me give you some tips, you are making progress though

you can't use a for loop like that because the number entered is not a number you go up to, its the total number or prime numbers, redo it with a while loop and a counter for primes found

here's enough to get you started

``````int num = Int32.Parse(Console.ReadLine());
int primesFound = 0;
int curNum =2;
while(primesFound < num)
{
bool isNotPrime = false;

//do your check for prime against curNum

if(isNotPrime == false)
{
//if curNum is prime number, print it...
Console.Write("{0} ", curNum);
// increment our prime counter
primesFound++;
}

curNum++;

}``````

CAN YOU HELP ME WITH THIS ONE ALSO!
2.Enter a string of numbers on the keyboard until we enter "0".
After that we need to print out the Arithmetic mean of the par numbers (ex: 2) and the impair numbers (ex: 3) that we entered earlier.

I've spend all day i can't make it!

does your prime number one work now?

now, do you finish your project? i can help you but i cant contact with you, can you send email for me? I will send my project about your problem for you. My email: linhlevandlu@gmail.com. Thank you.

Hope you enjoy the spam you'll get for posting your email on a bulletinboard readily searched by search engines.. Spammers are gonna love you.

Failing that you could start a new thread with your new question and explain it clearly, and more usefully explain the reason why you cant work it out.

Why not try it like this :
Make a list of primes
Print the n first numbers from the list.
This is the code to start with, you should be able to complete it.

``````using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;

namespace Primes
{
class Program
{
private static List<int> primes = new List<int>();

private static bool CheckIfPrime(int P)
{
bool Prime = true;
//You will not find any dividers of P greater than sqrt of P
//Unless you already found them as a result from a smaller one
int Q = Convert.ToInt32(Math.Sqrt(P));
foreach (int prime in primes)
{
if ((P % prime) == 0 && prime <= Q)
{
Prime = false;
break;
}
}
return Prime;
}

static void Main(string[] args)
{
//check the first 1000 integers for primeness
//can be changed to whatever until MaxInt
const int MaxVal = 1000;

// Add the first and only even prime to our list

// We don't have to check even numbers
// because we know they are not prime
for (int i = 3; i <= MaxVal; i += 2)
{
//fill in the primes list using our CheckIfPrime routine
}

//input a number here say n
//print out the first n numbers of the primes list
}
}
}``````

By the way. This algorithm was invented by a very old smart greek
and well known as "The sieve of Eratosthenes"

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