我已经开始学习code在Java和决定我会使用项目欧拉网站给我小任务，尝试和完成新的编码的每一位我学习。所以，我碰到问题3 ：

I have started learning to code in Java and decided I would use the Project Euler site to give me little tasks to try and complete with each bit of new coding I learn. So I came across Problem 3:

对13195的首要因素是5，7，13和29。 什么是数字600851475143的最大素因子？

The prime factors of 13195 are 5, 7, 13 and 29. What is the largest prime factor of the number 600851475143 ?

我想过这个问题，并研究了许多不同的理论，关于素数，以及他们如何可以通过各种不同的计算发现是从2测试号码 - >ñ看看他们是一个素数，如果是，那么我会分裂Tn的变量（在这种情况下600851475143）由新发现的素数，看看它是否是一个因素。如果是，我会把它赋值给变量马力（最高质数），并在节目我会输出马力到控制台给我结果的末尾。

I thought about the problem and researched many different theories about prime numbers and how they can be found via various different calculations (Sieve of Eratosthenes being an example) and the solution I conjured up was to test numbers from 2 --> n and see if they were a prime number, if they were then I would divide the Tn variable (in this case 600851475143) by the newly discovered prime number and see if it was a factor. If it was, I would assign it to the variable Hp (Highest Prime number) and at the end of the program I would output Hp to the console to give my result.

下面是我的code：

public class Largest_Prime_Factor_NEW_SOLUTION {

    static long Tn = 600851475143L;
    static long Hp = 0;
    static boolean isPrime = false;

    public static void main(String[] args) {

        for (long i=2; i<Tn; i++) {
            System.out.println("TESTING NUMBER " + i);
            for (long k=2; k < i; k++) {
                if (i % k == 0) {
                    System.out.println(i + " IS NOT A PRIME");
                    break;
                } else if (k + 1 == i) {
                    isPrime = true;
                }
            }

            if (isPrime) {
            System.out.println(i + " IS A PRIME");
            if (Tn % i == 0) {
                System.out.println(Tn + " IS DIVISIBLE BY " + i);
                Hp = i;
            } else {
                System.out.println(Tn + " IS NOT DIVISIBLE BY " + i);
            }
            }

            isPrime = false;
        }
        System.out.println("THE HIGHEST PRIME NUMBER OF " + Tn + " IS " + Hp);
    }
}

现在我知道，这code是非常低效和刚开始我已成功地从我开始（有循环无处不在！）凝结，但什么，我是问的是，我怎么能提高呢？它蚕食我，因为我的一切研究违背别人会怎么做，这是非常令人困惑。我曾尝试筛方法，但据我所知，布尔数组只能是一个int数组，从来没有一个多头排列？

Now I know that this code is very inefficient and for just starting I have managed to condense it from where I began (there were loops everywhere!) but what I am is asking is, how can I improve this? It's eating away at me because everything I research contradicts what others would do and it's very confusing. I have tried the sieve method but i understand that a boolean array can only be an int array and never a long array?

据我所知，开始code，当我将被限制到什么知识，我可以使用，但只是出于兴趣，我很希望看到最终的解决办法是。

I understand that when beginning to code I will be limited to what knowledge I can use, but just out of interest, I am keen to see what the final solution would be.

推荐答案

你可以做的就是找​​到 Tn的最低的约数。假如是 P ，再次找到最低的除数 TN / P> / code>等等。