Foro Oficial De C++

#include <iostream>
using namespace std;

int main ()
{
    int num, band = 0;
    cout <<"Introduce un numero entero: ";
    cin >> num;
    
    if ((num == 1) || (num == 2))
       cout<<"El numero es primo";
       
    else
    {
        for (int i = 2; i < num; i++)
        {
            if (num % i == 0)
               band = 1;
        }
    }
    
    if (band == 1)
       cout<<"No es un numero primo"<<endl;
    
    else
        cout<<"El numero es primo"<<endl;
}

#include <iostream>
using namespace std;

int main ()
{
    unsigned int num, i=2;
    cout<<"\nIntroduzca un numero entero positivo: ";
    cin >> num;
    cout<<" "<<endl;
    
    while (i <= num)
    
          if (num % i == 0)
          {
              cout<<""<<i<<" es un factor primo"<<endl;
              num = num/i;
          }
          else
              i++;         
}

#include <iostream>
using namespace std;

void criba (int [], int &, int);
int contar_primos (int [], int);

int main ()
{
    int n;
    cout << "Introduzca un numero entero: ";
    cin >> n;
    int v[n];
    
    if (n == 1)
       cout << "No hay primos" <<endl;
    
    else
    {
        for (int i = 0; i < n-1; i++)
            v[i] = i+2;
        
        for (int j = 0; (v[j]*v[j]) <= n; j++)
        {
            if (v[j] != 0)
               criba (v, v[j], n-1);
        }
    }
    
    cout << " "<<endl;
    cout << "Hasta el "<<n<<" hay "<<contar_primos(v,n)<<" numeros primos"<<endl;
    
    for (int a = 0; a < n-1; a++)
        if (v[a] != 0)
           cout << v[a] << " ";
    
    cout<<" "<<endl;
}

void criba (int v[], int &a, int lon)
{
     for (int i = 0; i < lon; i++)
         if (v[i] != 0)
			if (((v[i]%a) == 0) && ((v[i]/a) != 1))
				v[i] = 0;
}

int contar_primos (int v[], int a)
{
     int j = 0;
     
     for (int i = 1; i < a; i++)
         if (v[i] != 0)
            j++;
            
     return j;
}

#include <iostream>
using namespace std;

int main ()
{
    int i; 
    int num; 
    int long fact; 
    cout<<"Teclea un número para calcular su factorial: ";
    cin>>num;
    
    for (i=1, fact=1; i<=num; i++)
        fact*=i;
        
    cout<<"El factorial de "<<num<<" es "<<fact;
}