的StackOverflowError计算BigInteger的阶乘？ [英] StackOverflowError computing factorial of a BigInteger?

问题描述

我想写一个Java程序来计算大量的阶乘。这似乎的BigInteger 无法容纳这么大的数字。

I am trying to write a Java program to calculate factorial of a large number. It seems BigInteger is not able to hold such a large number.

下面是（简单的）code我写的。

The below is the (straightforward) code I wrote.

 public static BigInteger getFactorial(BigInteger num) {
      if (num.intValue() == 0) return BigInteger.valueOf(1);

      if (num.intValue() == 1) return BigInteger.valueOf(1);

      return num.multiply(getFactorial(num.subtract(BigInteger.valueOf(1))));
  }

在5022以上程序处理，之后，该计划抛出一个的StackOverflowError 的最大数量。是否有任何其他的方式来处理呢？

The maximum number the above program handles in 5022, after that the program throws a StackOverflowError. Are there any other ways to handle it?

推荐答案

这里的问题看起来像它的一个堆栈溢出从过多递归（5000递归调用看起来像有关呼叫权数吹出一个Java < A HREF =htt​​p://en.wikipedia.org/wiki/Call_stack>调用堆栈），而不是的BigInteger 。反复重写阶乘函数应该解决这个问题。例如：

The problem here looks like its a stack overflow from too much recursion (5000 recursive calls looks like about the right number of calls to blow out a Java call stack) and not a limitation of BigInteger. Rewriting the factorial function iteratively should fix this. For example:

public static BigInteger factorial(BigInteger n) {
    BigInteger result = BigInteger.ONE;

    while (!n.equals(BigInteger.ZERO)) {
        result = result.multiply(n);
        n = n.subtract(BigInteger.ONE);
    }

    return result;
}

希望这有助于！

Hope this helps!

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