蓝桥杯练习 用筛法求之N内的素数 线性素数筛

题目链接http://www.dotcpp.com/oj/problem1084.html

AC代码：

#include<iostream>
#include<cstring>
using namespace std;
const int maxn = 1e6+10;
//===================
int prime[maxn];
bool number[maxn];
int n,cnt;
void isprime(int n){    //1~n的素数
    memset(number, true, sizeof number);
    number[0]=number[1] = false;
    cnt = 0;
    for (int i = 2; i <= n; i++){
        if (number[i])
            prime[cnt++] = i;
        for (int j = 0; j < cnt&&prime[j] * i <= n; j++){
            number[prime[j] * i] = false;
            if (i%prime[j] == 0)
                break;
        }
    }
}
int main()
{
    cin >> n;
    isprime(n);
    for (int i = 0; i < cnt; i++){
        cout << prime[i] << endl;
    }
    return 0;
}

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