Hi, I know this kind of stuff been wandering around. I did have a look through the search function but I haven't got the answer.
This is the program to check whether the number inputted is a prime number or not.
#include <iostream>
#include <math.h>
#define TRUE 1;
#define FALSE 0;
using namespace std;
void getNumber(int*);
int isPrime(int);
int main()
{
int number;
getNumber(&number);
if (isPrime(number))
{
cout << "\n" << number << " is a prime number\n";
}
else
{
cout << "\n" << number << " is not a prime number\n";
}
system("PAUSE");
return 0;
}
void getNumber(int *number)
{
cout << "Please enter a positive number ";
cin >> *number;
if (!cin.good())
{
printf("Invalid number entered\n");
exit(1);
}
}
int isPrime(int number)
{
int count;
double s;
if (number > 0)
{
if (number != 1)
{
if (number != 2)
{
/* Every even number is not prime */
if (number % 2 == 0)
{
return FALSE;
}
else
{
/* check every odd number up to the square root of the number */
s = sqrt(number);
for (count=3; count<=s; count+=2);
{
cout << count << "<- This is the count";
if (number % count == 0)
return FALSE;
}
return TRUE;
}
}
else
{
return TRUE;
}
}
else
{
return FALSE;
}
}
else
{
cout << "You have entered negative number, please enter positive number only!\n";
exit(1);
}
}I've got problem with the for statement.
When I inputted 3 the program says 3 is not a prime number
but when I inputted 9, 21, 25, 27 it says they are prime number..
I tried to search google for the right prime number algorithm but didn't find anything useful.
Can someone help me? I think, the for statement suppose to check whether the number is divisible by 3, 5, 7 and so on...
