If you want to use recursion, it should be as simple as:
defmodule Solution do
def run([]), do: [true]
def run([head | tail]), do: [{head, run(tail)}]
end
Solution.run([:a, :b, :c, :d, :e, :f])
# [a: [b: [c: [d: [e: [f: [true]]]]]]]
xhh
2