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require "ext"
local parse_map = true
local map = {}
local row,col = 0,0
local start
local commands = {}
local face_size =
for line in io.lines() do
row = row + 1
if line ~= "" and parse_map then
col = 0
for char in line:gmatch("(.)") do
col = col + 1
local locf = string.format("%d,%d",row,col)
if char == "." then
if start == nil then
start = locf
end
map[locf] = true
elseif char == "#" then
map[locf] = false
end --else, it's nil
end
elseif line == "" and parse_map then
parse_map = false
elseif not parse_map then
local ccursor = line
while ccursor ~= "" do
if ccursor:find("^%d") then
table.insert(commands,{type="walk",n=ccursor:match("^(%d+)")})
ccursor = ccursor:gsub("^(%d+)","")
elseif ccursor:find("^[LR]") then
table.insert(commands,{type="turn",n=ccursor:match("^([LR])")})
ccursor = ccursor:gsub("^[LR]","")
end
end
end
end
local directions = {
up = {-1, 0},
down = {1,0},
left = {0,-1},
right = {0,1}
}
local dirmap = {
[0] = {
name = "right",
R = 1,
L = 3
},
[1] = {
name = "down",
R = 2,
L = 0
},
[2] = {
name = "left",
R = 3,
L = 1
},
[3] = {
name = "up",
R = 0,
L = 2
}
}
local mem_loop = {}
local function find_loop_loc(sloc, direction)
print("Finding loop location from",sloc,"dir",direction)
if mem_loop[sloc] and mem_loop[sloc][direction] then
return mem_loop[sloc][direction]
end
local srow, scol = sloc:match("(%d+),(%d+)")
local radd, cadd = -direction[1], -direction[2]
while map[string.format("%d,%d",srow,scol)] ~= nil do
print("Examining",string.format("%d,%d",srow,scol),"was not nil")
srow, scol = srow + radd, scol + cadd
end
print("Examining",string.format("%d,%d",srow,scol),"was nil")
local ret = string.format("%d,%d",srow + direction[1],scol + direction[2])
mem_loop[ret] = mem_loop[ret] or {}
mem_loop[ret][direction] = ret
print("Returning",ret)
return ret
end
print("map",map)
print("commands",commands)
local state = {
location = start,
direction = 0
}
print("Starting state:",state)
local function open(location,direction)
local crow, ccol = state.location:match("(%d+),(%d+)")
local rrow, rcol = crow + direction[1], ccol + direction[2]
local rloc = string.format("%d,%d",rrow,rcol)
if map[rloc] then
return true, rloc
elseif map[rloc] == false then
return false
else
local loop_loc = find_loop_loc(location,direction)
assert(map[loop_loc] ~= nil)
if map[loop_loc] then
return true, loop_loc
else
return false
end
end
end
local function run(state, instructions)
local function walk(state,n)
for i = 1, n do
local dir = directions[dirmap[state.direction].name]
local isopen, newloc = open(state.location,dir)
if isopen then
print("Walked to",newloc)
state.location = newloc
else
break
end
end
end
local function turn(state,dir)
state.direction = dirmap[state.direction][dir]
end
while #instructions > 0 do
local ins = table.remove(instructions,1)
if ins.type == "walk" then
walk(state,ins.n)
elseif ins.type == "turn" then
turn(state,ins.n)
end
end
end
run(state,commands)
print(state)
local row, col = state.location:match("(%d+),(%d+)")
print((row*1000) + (col * 4) + state.direction)
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