Question

我正在获取13195L，24L和23L的输出。但是我没有得到600851475143L的输出。系统进入无限循环。请帮助我确定我的代码有什么问题。

package problem3;

public class problem3_version1 {
    public static void main(String[] args) {
        long dividend = 600851475143L;
        // long dividend=13195L;
        // long dividend=24L;
        // long dividend=23L;
        int num_of_divisors = 0;
        for (long i = dividend - 1; i >= 2; i--) {
            System.out.println("i =" + i);
            int count = 2;
            for (long j = 2; j < i; j++) {
                if (i % j == 0)
                    count++;
                if (count == 3)
                    break;
            }
            if (count == 2) {
                if (dividend % i == 0) {
                    num_of_divisors++;
                    System.out.println("Highest factor is " + i);
                    break;
                }
            }
        }
        if (num_of_divisors == 0)
            System.out.println("The number is prime");
    }
}

Answer 1

尝试此解决方案：

public class LargestPrimeFactor 
{

    public static int largestPrimeFactor(long number) {
        int i;

        for (i = 2; i <= number; i++) {
            if (number % i == 0) {
                number /= i;
                i--;
            }
        }

        return i;
    }

    public static void main(String[] args) {
        System.out.println(LargestPrimeFactor.largestPrimeFactor(600851475143l));
    }

}

问题是因为您嵌套了数量很大的循环，而造成循环的原因

找到最大的素数为600851475143L

1 个答案: