题解 | #质数因子#

import java.util.Scanner;

// 注意类名必须为 Main, 不要有任何 package xxx 信息
public class Main {
    public static void main(String[] args) {
        Scanner scanner = new Scanner(System.in);
 
        long num = scanner.nextLong();
        long k = (long) Math.sqrt(num);
    
        for (long i = 2; i <= k; ++i) {
            while (num % i == 0) {
                System.out.print(i + " ");
                num /= i;
            }
        }
        System.out.println(num == 1 ? "": num+" ");
    }
    
}

涉及到while循环时，要注意看下循环结束的条件是否可优化，这往往会成为优化的关键