高效素数打表

#include <bits/stdc++.h>
#include <iostream>
#include <cstdio>
#include <algorithm>
#include <cmath>
#include <cstring>
#include <vector>
#include <map>
#include <set>
#include <bitset>
#include <queue>
#include <deque>
#include <stack>
#include <iomanip>
#include <cstdlib>
using namespace std;
#define is_lower(c) (c>='a' && c<='z')
#define is_upper(c) (c>='A' && c<='Z')
#define is_alpha(c) (is_lower(c) || is_upper(c))
#define is_digit(c) (c>='0' && c<='9')
#define min(a,b) ((a)<(b)?(a):(b))
#define max(a,b) ((a)>(b)?(a):(b))
#define IO ios::sync_with_stdio(0);
cin.tie(0);
cout.tie(0);
#define For(i,a,b) for(int i = a; i <= b; i++)
typedef long long ll;
typedef unsigned long long ull;
typedef pair<int,int> pii;
typedef pair<ll,ll> pll;
typedef vector<int> vi;
const ll inf=0x3f3f3f3f;
const double EPS=1e-10;
const ll inf_ll=(ll)1e18;
const ll maxn=100005LL;
const ll mod=1000000007LL;
const int N = 2000+5;

const int maxn 10000000
bool visit[maxn+1000000];
int prime[maxn],n;
void getprime()
{
memset(visit, false, sizeof(visit));
int num = 0;
for (int i = 2; i <= maxn; ++i)
{
if ( !visit[i] )
prime[++num] = i;
for (int j = 1; j <= num && i * prime[j] <= n ; j++)
{
visit[ i * prime[j] ] = true;
if (i % prime[j] == 0) break;
}
}
}
int main()
{
scanf("%d",&n);
getprime();
return 0;
}