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  1. defmodule Population do
  2.     def count_people(people) do
  3.         people
  4.             |> Enum.reduce(%{}, fn (%{ birth: birth, death: death }, acc) ->
  5.                 acc
  6.                     |> Map.update(birth, 1, &(&1 + 1))
  7.                     |> Map.update(death, -1, &(&1 - 1))
  8.             end)
  9.             |> Enum.scan({0, 0}, fn({ year, population }, { _, population_acc }) -> { year, population + population_acc } end)
  10.             |> Enum.max_by(fn({_, year}) -> year end)
  11.     end
  12. end
  13.  
  14. people = [
  15.   %{ birth: 1920, death: 1950 },
  16.   %{ birth: 1920, death: 1980 },
  17.   %{ birth: 1940, death: 1990 },
  18.   %{ birth: 1930, death: 1940 },
  19.   %{ birth: 1970, death: 2010 },
  20.   %{ birth: 1920, death: 1960 },
  21.   %{ birth: 1720, death: 1860 },
  22.   %{ birth: 1730, death: 1810 }
  23. ];
  24.  
  25. people
  26.     |> Population.count_people
  27.     |> IO.inspect
Success #stdin #stdout 0.4s 29956KB
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{1930, 4}
https://ideone.com/CLG933
language:
Elixir (elixir 1.8.2)
created:
7 years ago
visibility:
public

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