clean up with sign function

day05/part2.lua

@@ -10,13 +10,16 @@ function readline()
 	return x1, y1, x2, y2
 end
 
-function mark(field, x, y, count, dx, dy)
+function mark(field, x, y)
-	local i = 0
+	local row = field[x] or {}
-	while i <= count do
+	row[y] = (row[y] or 0) + 1
-		local row = field[x+i*dx] or {}
+	field[x] = row
-		row[y+i*dy] = (row[y+i*dy] or 0) + 1
+end
-		field[x+i*dx] = row
+
-		i = i + 1
+function sign(n)
+	if n == 0 then return 0
+	elseif n < 0 then return -1
+	else return 1
 	end
 end
 
@@ -24,15 +27,11 @@ io.input(arg[3])
 local x1, y1, x2, y2 = readline()
 local field = {}
 while x1 ~= nil do
-	local x, y, count, dx, dy
+	local x, y, dx, dy = x1, y1, sign(x2 - x1), sign(y2 - y1)
-	if x1 == x2 then
+	mark(field, x, y)
-		mark(field, x1, math.min(y1, y2), math.abs(y1 - y2), 0, 1)
+	while x ~= x2 or y ~= y2 do
-	elseif y1 == y2 then
+		x, y = x + dx, y + dy
-		mark(field, math.min(x1, x2), y1, math.abs(x2 - x1), 1, 0)
+		mark(field, x, y)
-	elseif x1 + y1 == x2 + y2 then
-		mark(field, math.min(x1, x2), math.max(y1, y2), math.abs(x1 - x2), 1, -1)
-	else
-		mark(field, math.min(x1, x2), math.min(y1, y2), math.abs(x1 - x2), 1, 1)
 	end
 	x1, y1, x2, y2 = readline()
 end