Question

当输入为25时，预期输出为15511210043330985984000000而非1.551121e+25。解析虽然由Decimal.Parse(factorial.ToString(), System.Globalization.NumberStyles.Float)解决。

我无法计算更大的数字，比如95。

using System;

namespace bigNumber
{
    class Program
    {
        static void Main(string[] args)
        {
            int number = Convert.ToInt32(Console.ReadLine());
            long factorial = 1;

            for (int i = number; i > 0; i--)
            {
                factorial = factorial * i;
            }

            Console.WriteLine(factorial);
        }
    }
}

Answer 1

您必须在解决方案中使用BigInteger：

using System.Numerics;
using System.Linq; 
...
int n = 95;

BigInteger factorial = Enumerable
  .Range(1, n)
  .Select(x => (BigInteger) x)
  .Aggregate((f, v) => f * v);

Console.WriteLine(factorial);

答案是

10329978488239059262599702099394727095397746340117372869212250571234293987594703124871765375385424468563282236864226607350415360000000000000000000000

请注意，factorial远远超出 long.MaxValue

Answer 2

如上所述，BigInteger是一个很好的候选者，因为它可以保存一个任意大的有符号整数：

namespace ConsoleApplication4
{
    using System;
    using System.Numerics;

    class Program
    {
        static void Main(string[] args)
        {
            Console.WriteLine(Factorial(0));

            Console.WriteLine(Factorial(25));

            Console.WriteLine(Factorial(95));
        }

        private static BigInteger Factorial(int number)
        {
            BigInteger factorial = 1;

            for (var i = number; i > 0; i--)
            {
                factorial *= i;
            }

            return factorial;
        }
    }
}

1
15511210043330985984000000
10329978488239059262599702099394727095397746340117372869212250571234293987594703124871765375385424468563282236864226607350415360000000000000000000000
Press any key to continue . . .

Answer 3

.Net 4.0+中的BigInteger类支持任意大整数，int相对限制它代表的有效位数。

将95阶乘打印为数字而不是指数函数

3 个答案: