Question

我正在解决项目Euler的问题10，通过添加自然数来生成三角数的序列。所以第7个三角形数字是1 + 2 + 3 + 4 + 5 + 6 + 7 = 28，要找到第一个三角形数的值超过500个除数？

我写了以下程序：

public class ProjectEulerProb12HighestDivisorTriangNumb {

  public static void main(String[] args) {

    int minLim = 7; //As seven is already given in prob statement
    System.out.println(
        "The first triangular no to have more than 500 divisors is " + getNaturalnumb(minLim));
  }

  public static int getNaturalnumb(int natNum) {
    int div = 1, TrianNum = 1;

    while (div <= 500) {
      natNum++;
      TrianNum = getTrianNum(natNum);
      div = getDivCount(TrianNum);
    }

    return TrianNum;
  }

  public static int getTrianNum(int n) { //Generating Triangular Number for any Natural no. n
    int TrianNum = 0;

    for (int i = 1; i <= n; i++) {
      TrianNum += i;
    }
    System.out.println(" The current TrianNum is " + TrianNum);
    return TrianNum;
  }

  public static int getDivCount(int n) {// Getting Divisor count for any Triangular no. n

    int DivCount = 1, nextnum = 1;

    while (n != nextnum || DivCount != 500) {
      if (n % nextnum == 0) {
        System.out.println(
            " The current n is "
                + n
                + " Current nextnum is "
                + nextnum
                + " current Divcount is "
                + DivCount);
        DivCount++;
      }

      nextnum++;
    }

    return DivCount;
  }
}

我遇到了运行时异常：

    Exception in thread "main" java.lang.ArithmeticException: / by zero
at ProjectEulerProb12HighestDivisorTriangNumb.getDivCount(ProjectEulerProb12HighestDivisorTriangNumb.java:47)
at ProjectEulerProb12HighestDivisorTriangNumb.getNaturalnumb(ProjectEulerProb12HighestDivisorTriangNumb.java:20)
at ProjectEulerProb12HighestDivisorTriangNumb.main(ProjectEulerProb12HighestDivisorTriangNumb.java:8)

要查看我错在哪里，我在方法getDivCount中输入print语句并得到以下输出：

    The current TrianNum is 36
    The current n is 36 Current nextnum is 1 current Divcount is 1
    The current n is 36 Current nextnum is 2 current Divcount is 2
    The current n is 36 Current nextnum is 3 current Divcount is 3
    The current n is 36 Current nextnum is 4 current Divcount is 4
    The current n is 36 Current nextnum is 6 current Divcount is 5
    The current n is 36 Current nextnum is 9 current Divcount is 6
    The current n is 36 Current nextnum is 12 current Divcount is 7
    The current n is 36 Current nextnum is 18 current Divcount is 8
    The current n is 36 Current nextnum is 36 current Divcount is 9
    The current n is 36 Current nextnum is -36 current Divcount is 10
    The current n is 36 Current nextnum is -18 current Divcount is 11
    The current n is 36 Current nextnum is -12 current Divcount is 12
    The current n is 36 Current nextnum is -9 current Divcount is 13
    The current n is 36 Current nextnum is -6 current Divcount is 14
    The current n is 36 Current nextnum is -4 current Divcount is 15
    The current n is 36 Current nextnum is -3 current Divcount is 16
    The current n is 36 Current nextnum is -2 current Divcount is 17
    The current n is 36 Current nextnum is -1 current Divcount is 18

    Exception in thread "main" java.lang.ArithmeticException: / by zero

为什么int值在满足条件（n！= nextnum）后递增为负值？帮助！

Answer 1

原因是你正在击中整数溢出。

如果您通过循环（n = 36），您会注意到DivCount = 9时nextnum = 36（即nextnum = n）。这意味着在此迭代中循环不会破坏。

在所有其他nextnum中，不等于n，然后进入无限循环，直到nextnum溢出并抛出异常。

Answer 2

由于我无法发表评论，我必须发布答案。我想补充一点：如果你需要非常大的数字，你需要使用BigInteger / BigDecimal等等 - 这也需要更多的代码来处理操作。但这是一个解决方案。

为什么int值增加到负值而不是中断给定的循环？

2 个答案: