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Factorial calculation of LARGE numbers...
By Love_U_JERRY, 11 years ago, In English

How to calculate factorial of larger integer numbers ( i.e. numbers greater than 20 ) using C/C++ using high precision arithmetic ?

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11 years ago, # |
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Implement big numbers. Like BigInteger in Java.

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11 years ago, # |
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Is there any algorithm can do this in O(logN) or less than O(N) ?

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    11 years ago, # ^ |
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    Factorial grows exponentially. So you need at least O(n) time and memory to calculate it precisely.

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      11 years ago, # ^ |
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      Also a^N grows exponentially but we can calculate it in O(logN)

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        11 years ago, # ^ |
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        You can calculate it fast unprecisely: either modulo some number or in floating-point type. Anyway, I haven't heard about any fancy factorial calculation algorithms that use less than O(n) arithmetic operations.

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