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Help! Prime Number

 
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Help! Prime Number
kavi
3 Nov, 2006 - 10:27 AM
Post #1

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I need help!!

I Can not invent the algorithm of this programm. Can someone help me? smile.gif

input number "n" and the programm shows all prime number who is lesser than number "n" and whom can enounce like 2^k -1

This post has been edited by kavi: 3 Nov, 2006 - 10:38 AM
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Jayman
RE: Help! Prime Number
3 Nov, 2006 - 10:37 AM
Post #2

Student of Life
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Post the code you have completed so far and someone will be happy to help you.
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kavi
RE: Help! Prime Number
3 Nov, 2006 - 10:47 AM
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CODE
#include <iostream>
int x (int n,int m); //deklaree visus mainiigos
using namespace std;

int main()
{
    int n, m=0;
    char exit;
    do
    {
         cout << "\nInput number, \nthe programm will show \nall prime number who is \nlesserthan your input number \nand which can enounce like 2^k -1 ";
         cin  >> n;
         cout << "\nYour input number is : "  << n << endl;
        
         ................................. <<< I can`t  invent what be writen in here
        
         cout << "\nPrime number wich is lesser than your nummber and \nwich enounce like 2^k -1 is  : "  << m << endl;
         cout << "\nRepeat the programm <y/n> " << endl;
         cin  >> exit;
    }
while (exit=='y');

return 0;
}
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Dark_Nexus
RE: Help! Prime Number
3 Nov, 2006 - 02:13 PM
Post #4

or something bad...real bad.
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a prime number is a number which is divisible only by itself and one

thus the following algorithm, should verify whether a number is prime or not

CODE


bool isPrime(int num)
{
     for (int i = 2;i < num;++i)
     {
          if (num % i == 0)
               return false;
     }

     return true;
}
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born2c0de
RE: Help! Prime Number
4 Nov, 2006 - 03:17 AM
Post #5

printf("I'm a %XR",195936478);
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QUOTE
a prime number is a number which is divisible only by itself and one

or you can write the function using the exact definition that Dark_Nexus gave:
CODE

int isprime(int x)
{
   int i=2;
   while(x%i)i++;

   return (x==i);
}
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