Advent of Code 2019 - Lua
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rocks = {}
pos_y = 0
for line in io.lines(arg[1]) do
pos_x = 0
for char in line:gmatch(".") do
if char == "#" then
table.insert(rocks, {y=pos_y, x=pos_x})
end
pos_x = pos_x + 1
end
pos_y = pos_y + 1
end
pos_y = nil
pos_x = nil
max = nil
for _, rock in ipairs(rocks) do
count = 0
angles_array = {}
angles = {}
for _, in_rock in ipairs(rocks) do
if rock ~= in_rock then
angle = math.atan(in_rock.y - rock.y, in_rock.x - rock.x) + math.pi / 2
if angle < 0 then
angle = angle + math.pi * 2
end
if angles[angle] == nil then
angles[angle] = {in_rock}
table.insert(angles_array, angle)
count = count + 1
else
table.insert(angles[angle], in_rock)
end
end
end
if not max or max.count < count then
max = {count=count, rock=rock, angles=angles, angles_array=angles_array}
end
end
print(string.format("Part 1: %d (%d,%d)", max.count, max.rock.x, max.rock.y))
table.sort(max.angles_array)
for _, angle in ipairs(max.angles_array) do
table.sort(max.angles[angle], function(x, y)
local dist_x = math.sqrt((x.x - max.rock.x) ^ 2 + (x.y - max.rock.y) ^ 2)
local dist_y = math.sqrt((y.x - max.rock.x) ^ 2 + (y.y - max.rock.y) ^ 2)
return dist_x < dist_y
end)
end
shot = 0
while true do
for _, angle in ipairs(max.angles_array) do
if #max.angles[angle] > 0 then
shot = shot + 1
if shot >= 200 then
rock = max.angles[angle][#max.angles[angle]]
print(string.format("Part 2: %d", rock.x * 100 + rock.y))
os.exit(true)
end
max.angles[angle][#max.angles[angle]] = nil
end
end
end