Sieve of Eratosthenes

Prime generator with sieve Algo:

Tutorial (ENG)
shafaet tutorial (bangla)





Code:

	#include<bits/stdc++.h>
	using namespace std;
	bool a[11000000];
	void siv(){
	int n = 10000000;
	memset(a,true,sizeof(a));
	a[1]=false;
	for(int i=4;i<=n;i=i+2){
	a[i]=false;
	}
	int root = sqrt(n);
	for(int i=3;i<=root;i=i+2){
	if(a[i]==true){
	for(int j=i*i;j<=n;j=j+i){
	a[j]=false;
	}
	}
	}
	}
	int main(){
	siv();
	int n;
	cout<<"Enter a number: ";
	cin>>n;
	if(a[n]) cout<<"prime\n";
	else cout<<"not prime\n";
	}

view raw Sieve of Eratosthenes.cpp hosted with ❤ by GitHub