Question

write a program to display the prime numbers.

Answer 1

#include <cstdlib>
#include <iostream>
using namespace std;
int main()
{
int i, j,S; //index
int N; //size of array
bool *mas; //bool array

cout << "Prime numbers till N \n";
cout << "Enter number N ";
cin >> S;
N=S+1;
mas= new bool [N]; //dynamic array N

for(i=1; i<=S; i++) mas[i]=true;

for(i=2; ((i*i)<=S); i++)
if(mas[i])
for(j=(i*i); j<=S; j+=i)
if(mas[j]) mas[j]=false;

//print array
for(i=1; i<=S; i++)
if(mas[i]) cout << i << " ";


system("pause");
return 0;

system("PAUSE");
return EXIT_SUCCESS;
}