题目：将一个正整数分解质因数。例如：输入90,打印出90=2*3*3*5。

1.输入一个正整数n;
2.for循环
    2.1 定义k从2开始自增到k<=n;
    2.2 if判断        2.2.1,如果n%k==0,输出k;
        2.2.2 n=n/k;
        2.2.3 重新定义k=2;
   2.3输出最后一个质因数n;

[Java] 纯文本查看 复制代码

import java.util.ArrayList;

public class Demo_test00 {
    public static void main(String[] args) {

        foo(90L);
    }

    private static void foo(Long num) {

        if (num == 0 || num == 1) {
            System.out.println(num + "没有质因数");
            return;
        }

        long original = num;
        int count = 0;

        ArrayList<String> arrayList = new ArrayList<String>();

        for (long i = 2; i <= num; i++) {
            if (num % i == 0) {
                arrayList.add(Long.toString(i));
                count++;
                num /= i;
                i--;
            }
        }
        if (count < 2) {
            System.out.println(original + "为质数");
        } else {
            System.out.print(original + " = " + arrayList.get(0));
            for (int i = 1; i < count; i++) {
                System.out.print(" * " + arrayList.get(i));
            }
            System.out.printf("\n%d共有%d个质因数\n", original, count);
        }
    }
}

香草芭芙 发表于 2017-2-22 14:23
[mw_shl_code=java,true]import java.util.ArrayList;

public class Demo_test00 {

我去试试去，谢谢啦