Implementation of A classical Way of generating the prime numbers between 1 to n using Seive of Erothenus Algorithm.

Seiveoferothenus.cpp

#include<bits/stdc++.h>
using namespace std;
typedef long long int lli;
typedef long long ll;
#define fi(i,n) for(int i=0;i<n;i++)
#define Fi(i,k,n) for(int i=k;i<n;i++)
#define fd(i,n) for(int i=n-1;i>=0;i--)
#define Fd(i,k,n) for(int i=n-1;i>=k;i--)
#define pop(i) __builtin_popcount(i)
const int mod = 1000000007;
#define deb(x) cout<<#x<<" "<<x<<"\n"
#define PI 3.1415926535897932384626
#define all(x) x.begin(),x.end()
#define sortall(x) sort(all(x))
#define mp make_pair
typedef pair<int,int> pii;
typedef pair<ll,ll> pll;
#define F first
#define S second
#define itr(it,a) for(it=a.begin();it!=a.end();it++)
#define bs(a,b) binary_search(all(a),b)
#define lb(a,b) lower_bound(all(a),b)
#define ub(a,b) upper_bound(all(a),b)
#define nod(x) floor(log10(x))+1
#define pb(s) push_back(s)
void SieveOfEratosthenes(int n) 
{ 
    // Create a boolean array "prime[0..n]" and initialize 
    // all entries it as true. A value in prime[i] will 
    // finally be false if i is Not a prime, else true. 
    bool prime[n+1]; 
    memset(prime, true, sizeof(prime)); 
  
    for (int p=2; p*p<=n; p++) 
    { 
        // If prime[p] is not changed, then it is a prime 
        if (prime[p] == true) 
        { 
            // Update all multiples of p greater than or  
            // equal to the square of it 
            // numbers which are multiple of p and are 
            // less than p^2 are already been marked.  
            for (int i=p*p; i<=n; i += p) 
                prime[i] = false; 
        } 
    } 
  
    // Print all prime numbers 
    for (int p=2; p<=n; p++) 
       if (prime[p]) 
          cout << p << " "; 
} 
int main(){
    int size=1000000;
    SieveOfEratosthenes(size);
}