Java solution to Project Euler Problem 20

Problem 20:

n! means n * (n – 1) * … * 3 * 2 * 1

For example, 10! = 10 * 9 * … * 3 * 2 * 1 = 3628800,
and the sum of the digits in the number 10! is 3 + 6 + 2 + 8 + 8 + 0 + 0 = 27.

Find the sum of the digits in the number 100!

Running time: 2ms

Assessment: Easy and fast using arbitrary-precision arithmetic.

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