adventofcode-2021/day17/part2.lua

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2021-12-17 10:03:15 +01:00
#!/usr/bin/env luajit
require("utils")
local xmin, xmax, ymin, ymax = string.match(io.open(arg[3]):read("*a"), "target area: x=(.*)%.%.(.*), y=(.*)%.%.(.*)")
xmin, xmax, ymin, ymax = tonumber(xmin), tonumber(xmax), tonumber(ymin), tonumber(ymax)
local mindy = ymin
local maxdy = 0
if ymax > 0 then maxdy = ymax end
if ymin < 0 then if -ymin - 1 > maxdy then maxdy = -ymin - 1 end end
local mindx = 0
while euler(mindx) < xmin do mindx = mindx + 1 end
local maxdx = xmax
local count = 0
for odx = mindx, maxdx do
for ody = mindy, maxdy do
local x, y, dx, dy = 0, 0, odx, ody
while x <= xmax and y >= math.min(0, ymin) do
x, y = x + dx, y + dy
if xmin <= x and x <= xmax and ymin <= y and y <= ymax then
count = count + 1
break
end
if dx > 0 then dx = dx - 1 end
dy = dy - 1
end
end
end
print(count)