population = for _ <- 1..10, do: for _ <- 1..42, do: Enum.random(0..1)

evaluate = fn population ->
  Enum.sort_by(population, &Enum.sum(&1), &>=/2)
end

selection = fn population ->
  population
  |> Enum.chunk_every(2)
  |> Enum.map(&List.to_tuple(&1))
end

crossover = fn population ->
  Enum.reduce(population, [], fn {p1, p2}, acc ->
    cx_point = :rand.uniform(42)
    {{h1, t1}, {h2, t2}} = {Enum.split(p1, cx_point), Enum.split(p2, cx_point)}
    [h1 ++ t2 | [h2 ++ t1 | acc]]
  end)
end

algorithm = fn population, algorithm ->
  best = Enum.max_by(population, &Enum.sum(&1))
  IO.write("\rCurrent Best: " <> Integer.to_string(Enum.sum(best)))
  if Enum.sum(best) == 42 do
    best
  else
    population
    |> evaluate.()
    |> selection.()
    |> crossover.()
    |> algorithm.(algorithm)
  end
end

solution = algorithm.(population, algorithm)
IO.write("\n Answer is \n")
IO.inspect solution

-population = for _ <- 1..10, do: for _ <- 1..42, do: Enum.random(0..1)
+problem_size = 42
+population_size = 100
+
+population = for _ <- 1..population_size, do: for _ <- 1..problem_size, do: Enum.random(0..1)

 evaluate = fn population ->
   Enum.sort_by(population, &Enum.sum(&1), &>=/2)
 end

 selection = fn population ->
   population
   |> Enum.chunk_every(2)
   |> Enum.map(&List.to_tuple(&1))
 end

 crossover = fn population ->
   Enum.reduce(population, [], fn {p1, p2}, acc ->
-    cx_point = :rand.uniform(42)
+    cx_point = :rand.uniform(problem_size)
     {{h1, t1}, {h2, t2}} = {Enum.split(p1, cx_point), Enum.split(p2, cx_point)}
     [h1 ++ t2 | [h2 ++ t1 | acc]]
   end)
 end

 algorithm = fn population, algorithm ->
   best = Enum.max_by(population, &Enum.sum(&1))
   IO.write("\rCurrent Best: " <> Integer.to_string(Enum.sum(best)))
-  if Enum.sum(best) == 42 do
+  if Enum.sum(best) == problem_size do
     best
   else
     population
     |> evaluate.()
     |> selection.()
     |> crossover.()
     |> algorithm.(algorithm)
   end
 end

 solution = algorithm.(population, algorithm)
 IO.write("\n Answer is \n")
 IO.inspect solution