[Java] 蓝桥杯ADV-184 算法提高素数求和

问题描述
输入一个自然数n，求小于等于n的素数之和
样例输入
2
样例输出
2
数据规模和约定
测试样例保证 2 <= n <= 2,000,000

package adv184;

import java.util.Scanner;

public class Main {

    public static void main(String[] args) {
        Scanner in = new Scanner(System.in);
        int n = in.nextInt();
        boolean[] prime = new boolean[n+1];
        in.close();
        setPrime(prime);
        long sum = 0;
        for (int i = 2; i < prime.length; i++) {
            if (prime[i]) {
                sum += i;
            }
        }
        
        System.out.println(sum);
    }

    private static void setPrime(boolean[] prime) {
        for (int i = 2; i < prime.length; i++) {
            prime[i] = true;
        }
        
        for (int i = 2; i < prime.length; i++) {
            for (int j = 2; i * j < prime.length; j++) {
                prime[i * j] = false;
            }
        }
    }
}

package adv184;

import java.util.Scanner;

public class Main {

public static void main(String[] args) {

Scanner in = new Scanner(System.in);

int n = in.nextInt();

boolean[] prime = new boolean[n+1];

in.close();

setPrime(prime);

long sum = 0;

for (int i = 2; i < prime.length; i++) {

if (prime[i]) {

sum += i;

}

System.out.println(sum);

}

private static void setPrime(boolean[] prime) {

for (int i = 2; i < prime.length; i++) {

prime[i] = true;

}

for (int i = 2; i < prime.length; i++) {

for (int j = 2; i * j < prime.length; j++) {

prime[i * j] = false;

}