Clean up day 18

2023/18_digplan.py

@@ -1,32 +1,19 @@
 #!/usr/bin/env python3
 import sys
-from itertools import pairwise
+from itertools import accumulate, pairwise
 
-def parse(inp):
-    DXDY = (1, 0), (0, 1), (-1, 0), (0, -1)
-    for line in inp:
-        direction, distance, color = line.split()
-        normal_instruction = DXDY['RDLU'.index(direction)], int(distance)
-        color_instruction = DXDY[int(color[7])], int(color[2:7], 16)
-        yield normal_instruction, color_instruction
+def parse(line):
+    direction, distance, color = line.split()
+    d = int(distance)
+    yield ((d, 0), (0, d), (-d, 0), (0, -d))['RDLU'.index(direction)]
+    d = int(color[2:7], 16)
+    yield ((d, 0), (0, d), (-d, 0), (0, -d))[int(color[7])]
 
-def follow(instructions):
-    x = y = 0
-    for (dx, dy), distance in instructions:
-        x += dx * distance
-        y += dy * distance
-        yield x, y
+def dig(steps):
+    xy = list(zip(*map(accumulate, zip(*steps))))
+    return sum(xa * yb - ya * xb + abs(xb - xa + yb - ya)
+               for (xa, ya), (xb, yb) in pairwise(xy + xy[:1])) // 2 + 1
 
-def dig(instructions):
-    x, y = zip(*follow(instructions))
-    v = len(x)
-    area = abs(sum(x[i] * y[(i + 1) % v] - y[i] * x[(i + 1) % v]
-                   for i in range(v))) // 2  # Shoelace formula
-    outer = sum(abs(bx - ax + by - ay)
-                for (ax, ay), (bx, by) in pairwise(zip(x + x[:1], y + y[:1])))
-    inner = area - outer // 2 + 1  # Pick's theorem
-    return outer + inner
-
-normal, color = zip(*parse(sys.stdin))
-print(dig(normal))
+wrong, color = zip(*map(parse, sys.stdin))
+print(dig(wrong))
 print(dig(color))