Problem 1

Problem

If we list all the natural numbers below \(10\) that are multiples of \(3\) or \(5\), we get \(3, 5, 6\) and \(9\). The sum of these multiples is \(23\).

Find the sum of all the multiples of \(3\) or \(5\) below \(1000\).

Julia

function p1()
  [x for x ∈ 1:999 if (x % 3 == 0 || x % 5 == 0)] |> sum
end;

p1()

233168

using BenchmarkTools;
@benchmark p1()

BenchmarkTools.Trial: 10000 samples with 8 evaluations.
 Range (min … max):  3.540 μs … 258.099 μs  ┊ GC (min … max): 0.00% … 95.67%
 Time  (median):     3.712 μs               ┊ GC (median):    0.00%
 Time  (mean ± σ):   4.299 μs ±   5.918 μs  ┊ GC (mean ± σ):  4.68% ±  3.41%
  ▅██▆▄▂▁▁▁▁     ▂▄▅▄▄▃▂▂▃▂▂▁                                 ▂
  ████████████▇▇▆█████████████████▇▇▇▆▇▇███▆▆▅▅▆▆▅▆▄▆▅▄▄▄▅▄▃▄ █
  3.54 μs      Histogram: log(frequency) by time      7.05 μs <
 Memory estimate: 7.61 KiB, allocs estimate: 6.