advent-of-code/12022/17/17.lua

--io.input("test")
io.input("input")
--
--local target = 2022 -- part 1
local target = 1000000000000 -- part 2

local shapes = {
  { w = 4, h = 1, map = { {1, 1, 1, 1} } },
  { w = 3, h = 3, map = { {0, 1, 0}, {1, 1, 1}, {0, 1, 0} } },
  { w = 3, h = 3, map = { {1, 1, 1}, {0, 0, 1}, {0, 0, 1} } },
  { w = 1, h = 4, map = { {1}, {1}, {1}, {1} } },
  { w = 2, h = 2, map = { {1, 1}, {1, 1} } },
}


local f = io.read("a")

local jets = {}
for j in string.gmatch(f,"[<>]") do
  table.insert( jets, j)
end

function emptiness()
  return {0, 0, 0, 0, 0, 0, 0}
end

local tunnel = {}

function tunnel:print()
  for i = #self, 1, -1 do
    local s = ""
    local row = self[i]
    for _, c in ipairs(row) do
      s = s .. (c == 1 and "@" or ( c==2 and "#" or "."))
    end
    print(s)
  end
end

function tunnel:drawShape( shape, shX, shY, color)
  local tunnel = self
  local color = color or 1
  for ly = 1, shape.h  do
    local y = ly + shY - 1
    tunnel[y] = tunnel[y] or emptiness()
    for lx = 1, shape.w do
      local x = lx + shX - 1
      tunnel[y][x] = shape.map[ly][lx]==1 and color or tunnel[y][x]
    end
  end
end

function tunnel:clearShape( shape, shX, shY )
  self:drawShape( shape, shX, shY, 0 )
end

function equals( t1, t2 )
  for i = 1, #t1 do
    if t1[i] ~= t2[i] then return false end
  end
  return true
end

local shI = 1
local jeI = 1
local erasedRows = 0
local iFound, iPeriod

local i = 1
while i <= target do
  local shape = shapes[shI]
  local x = 3 -- left
  local y = #tunnel + 4 -- bottom
  for i = 1, 3 do
    table.insert( tunnel, emptiness() )
  end

  repeat -- moving loop
    tunnel:drawShape( shape, x, y )

    -- jet
    local jet = jets[jeI]   
    local inc = jet=="<" and -1 or 1
    local canMove = false
    if (inc == -1 and x > 1 ) or ( inc == 1 and x + shape.w - 1 < 7) then
      canMove = true
      for lx = 1, shape.w do
        local shX = lx + x - 1
        for ly = 1, shape.h do
          local shY = ly + y - 1
          if tunnel[shY][shX+inc] == 2 and shape.map[ly][lx]==1 then
            canMove = false
          end
        end
      end
    end

    if canMove then
      tunnel:clearShape( shape, x, y )
      x = x + inc
      tunnel:drawShape( shape, x, y )
    end

    jeI = (jeI == #jets) and 1 or (jeI + 1)

    -- down
    canMove = (y > 1)
    if canMove then
      for lx = 1, shape.w do
        local shX = lx + x - 1
        for ly = 1, shape.h do
          local shY = ly + y - 1
          if tunnel[shY-1][shX] == 2 and shape.map[ly][lx]==1 then
            canMove = false
            break
          end
        end
        if not canMove then break end 
      end
    end

    if canMove then
      tunnel:clearShape( shape, x, y )
      y = y - 1
      tunnel:drawShape( shape, x, y )
    end
  until not canMove 
  
  -- stopped shape
  tunnel:drawShape( shape, x, y, 2)

  -- clean tunnel
  repeat
    local emptyRow = true
    local ind = #tunnel
    for _, c in ipairs( tunnel[ind] ) do
      if c > 0 then
        emptyRow = false
        break
      end
    end
    if emptyRow then
      table.remove( tunnel )
    end
  until not emptyRow or #tunnel == 0

  -- check for repetition
  local period
  for size = 10, #tunnel/2 do
    local equal = true
    for j = 1, size do
      local tail = tunnel[ #tunnel - j + 1 ]
      local tail2 = tunnel[ #tunnel - size - j + 1 ]
      if not equals(tail, tail2) then
        equal = false
        break
      end
    end
    if equal then 
      period = size

      for i = 1,period do
        table.remove(tunnel)
      end
      erasedRows = erasedRows + period

      if not iFound then 
        iFound = i 
      elseif not iPeriod then
        iPeriod = i - iFound
        -- jump ahead!
        local remaining = target - i
        local advance = remaining // iPeriod
        local outOfIPeriod = remaining % iPeriod
        erasedRows = erasedRows + advance*period
        i = target - outOfIPeriod
      end
     -- print(i, iFound, period, iPeriod, #tunnel )

      break
    end
  end

  shI = (shI == #shapes) and 1 or (shI + 1)

  i = i + 1
end

print("result ", #tunnel + erasedRows)