On Feb 12, 10:11 pm, Dave <[EMAIL PROTECTED]> wrote: > On Feb 12, 8:17 pm, "[EMAIL PROTECTED]" > <[EMAIL PROTECTED]> wrote: > > how will u find the "number of digits in the factorial of a number" > > without finding the factorial??- Hide quoted text - > > Sum log 1 + log 2 + log 3 + ... + log n, where log represents the > base-10 logarithm function. The ceiling of the sum gives the number of > digits.
True. Or if you want a close answer fast, you can use Stirling's approximation: ln n! = n lg n - n + 1 These are natural logs. To get log_10, just multiply by (lg e / lg 10) = (1 / lg 10). This apparently gives answers within 1 digit even for small n. If you need better accuracy, you can use more terms from Stirling's series. See for example http://mathworld.wolfram.com/StirlingsApproximation.html --~--~---------~--~----~------------~-------~--~----~ You received this message because you are subscribed to the Google Groups "Algorithm Geeks" group. To post to this group, send email to algogeeks@googlegroups.com To unsubscribe from this group, send email to [EMAIL PROTECTED] For more options, visit this group at http://groups.google.com/group/algogeeks -~----------~----~----~----~------~----~------~--~---
