Sieve-All Primes from 2 to n

/* Bismillahir Rahmanir Rahim Sieve-all primes from 1 to n */ #include<bits/stdc++.h> #define ll long long using namespace std; bool ar[10000009]; void sieve(ll x){ for(int i=3; i*i<=x; i+=2){ if(ar[i]){ for(int j=i*3; j<=x; j+=i*2) ar[j]=false; } } } int main(){ ll n, k; while(cin>>n){ memset(ar, true, sizeof(ar)); sieve(n); cout<<2<<" "; for(k=3; k<=n; k+=2){ if(ar[k])cout<<k<<" "; } cout<<endl; } return 0; }