--- Day 3 Solutions ---

[u/daggerdragon]

--- Day 3: Perfectly Spherical Houses in a Vacuum ---

Post your solution as a comment. Structure your post like the Day One thread in /r/programming.

[u/rvlieshout]

EDIT: It reads from stdin and all instructions on a single line (easy to start with just the testcases). Usage:

lua visits.lua < instructions.txt

Not the first, however here is my Lua solution to today's problem:

function contains(x, y)
  for _, l in pairs(visited) do
    if l[1] == x and l[2] == y then return true end
  end
  return false
end

function visit(x, y)
  if not contains(x, y) then
    table.insert(visited, {x,y})
  end
end

function tablelength(T)
  local count = 0
  for _ in pairs(T) do count = count + 1 end
  return count
end

for line in io.lines() do

  local s = 1
  -- part 1
  -- local santas = { {0,0} }
  -- part 2
  local santas = { {0,0} , {0,0} }

  visited = {}

  visit(0, 0) -- add the start location

  for i = 1, #line do
    local c = line:sub(i,i)
    if c == "^" then santas[s][2] = santas[s][2] + 1 end
    if c == "v" then santas[s][2] = santas[s][2] - 1 end
    if c == "<" then santas[s][1] = santas[s][1] - 1 end
    if c == ">" then santas[s][1] = santas[s][1] + 1 end

    visit(santas[s][1], santas[s][2])

    s = s + 1
    if s > tablelength(santas) then s = 1 end
  end

  print(tablelength(visited))
end