最小质因子之和（JAVA）线性筛

最小质因子，有埃式筛，但是埃式筛时间复杂度太高，用线性筛
线性筛是埃式筛的优化，减少了重复赋值，就是改变了顺序。

//package com.js.datastructure.recursion.蓝桥;import java.util.ArrayList;
//import java.util.Collection;
import java.util.Scanner;public class Main {public static void main(String[] args) {Scanner scanner = new Scanner(System.in);//先求最小质因子，再求前缀和long[] minp = new long[20000001];//minp[1] = 1;ArrayList<Integer> p = new ArrayList<>();  //存放质数for (int i = 2; i < 20000001; i++) {if(minp[i] == 0){p.add(i);minp[i] = i;}for (int pp : p) {if(i * pp >= 20000001){break;}minp[i * pp] = pp;if(minp[i] == pp){break;}}}//求前缀和for (int i = 2; i <= 20000000; i++) {minp[i] = minp[i-1] + minp[i];}int t = scanner.nextInt();//测试数据得出for (int i = 0; i < t; i++) {int n = scanner.nextInt();System.out.println(minp[n]);}}
}