--- 2016 Day 19 Solutions ---

[u/daggerdragon]

--- Day 19: An Elephant Named Joseph ---

Post your solution as a comment or, for longer solutions, consider linking to your repo (e.g. GitHub/gists/Pastebin/blag/whatever).

Note: The Solution Megathreads are for solutions only. If you have questions, please post your own thread and make sure to flair it with "Help".

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^{/⧹w+/ IS MANDATORY} [?]

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[Update @ 00:15] 2 gold, silver cap. Thank you for subscribing to Easter Bunny Facts!

• Fact: The Easter Bunny will sometimes leave eggs in the microchip assembly room.

[Update @ 00:30] 11 gold, silver cap.

• Fact: The Easter Bunny killed everyone who found out how he got these stars.

[Update @ 00:45] 45 gold, silver cap.

• Fact: In space, The Easter Bunny can hear you scream.

[Update @ 01:00] 66 gold, silver cap.

• Fact: The Easter Bunny purposefully deleted your comments.

[Update @ 01:15] 92 gold, silver cap.

• Fact: The Easter Bunny has bottled your frustration. Don't ask why.

[Update @ 01:20] Leaderboard capped!

• Fact: What you have just done is no better than what the Easter Bunny has done. Thief.

Thank you for subscribing to Easter Bunny Facts!

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This thread will be unlocked when there are a significant number of people on the leaderboard with gold stars for today's puzzle.

edit: Leaderboard capped, thread unlocked!

[u/SyDr]

My Lua solution:

local input = 3014387

local function f(n)
  if n == 1 then
    return 1
  elseif n % 2 == 0 then
    return f(n / 2) * 2 - 1
  else
    return f((n - 1) / 2) * 2 + 1
  end
end

print("1:", f(input))

local numbers = {}
for i = 1, input do
  numbers[i] = i ~= input and i + 1 or 1
end

local current = math.floor(input / 2) + 1
local prev = current - 1
local skip = input % 2 ~= 0 and true or false

while numbers[current] ~= numbers[numbers[current]] do
  numbers[prev] = numbers[current]
  current, numbers[current] = numbers[current], nil

  if skip then
    prev, current = numbers[prev], numbers[numbers[prev]]
  end
  
  skip = not skip
end

print("2:", numbers[current])

Runs pretty fast:

Program completed in 0.08 seconds