算术基本定义秒了

import java.util.*;

// 建立质数表
public class Main {
    public static void main(String[] args) {
        Scanner in = new Scanner(System.in);
        int n = in.nextInt(), prim;
        if(n == 1){// 1既不是素数也不是合数
            return;
        }
        if(n <= 3){
            System.out.println(n);
            return;
        }
        // 先建立质数表
        TreeSet<Integer> table = new TreeSet<>();
        int sq = (int)Math.sqrt(n);
        for(int i = 2; i <= sq; ++i){
            if(isPrim(i))table.add(i);
        }
        // 根据质数表从小到大尝试
        Iterator<Integer> it = table.iterator();
        prim = it.next();
        while(n > 1){
            if(n % prim == 0){
                System.out.print(prim+" ");
                n /= prim;
            }else if(it.hasNext()){
                prim = it.next();
            }else{// n 为 质数
                System.out.print(n);
                break;
            }
        }
    }

    // 判断n >= 2是否为质数
    public static boolean isPrim(int n){
        if(n <= 1)return false;
        if(n == 2)return true;
        int sq = (int)Math.sqrt(n);
        for(int e = 2; e <= sq; ++e){
            if(n%e == 0)return false;
        }
        return true;
    }
}