Prob 0020 ‐ Factorial Digit Sum - maccergit/Euler GitHub Wiki

Another quick one made super easy by Python.

01

Direct approach - compute $100!$, then convert to string, then iterate through string, convert each character back to a number, and sum them all up. The factorial is simply the product of the numbers 1..limit. This is so fast, we can go well beyond the stated problem :

02

The standard Python math library includes a factorial function that turns out to be a bit faster than rolling our own :