Calculate the Factorial of an Integer in C# 转 武胜

Calculate the Factorial of an Integer in C#

By Andrew Rissing, 18 Oct 2011

5.00 (8 votes)

 

 

 

Or you could just go the other direction and cache the known results ahead of time. You're only looking at 13 numbers in all, so it is not a big memory hog to just store those known values inside of the method and be done with it.
 

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static uint Factorial(uint x)
{
  if (x > 12)
    throw new ArgumentException("Cannot calculate a factorial for numbers larger than 12");
  return _factorials[x];
}
static readonly uint[] _factorials = new uint[13] { 1, 1, 2, 6, 24, 120, 720, 5040, 40320, 362880, 3628800, 39916800, 479001600 };