day 12

r0f1 · r0f1 · commit 595293fa7d27 · 2020-12-12T08:45:23.000+01:00
diff --git a/README.md b/README.md
@@ -13,7 +13,7 @@
 |[09](https://adventofcode.com/2020/day/9)|Encoding Error|[py](/day09/main.py)|
 |[10](https://adventofcode.com/2020/day/10)|Adapter Array|[py](/day10/main.py), [alt](/day10/alt.py)|
 |[11](https://adventofcode.com/2020/day/11)|Seating System|[py](/day11/main.py)|
-|[12](https://adventofcode.com/2020/day/12)|-|-|
+|[12](https://adventofcode.com/2020/day/12)|Rain Risk|[py](/day12/main.py)|
 |[13](https://adventofcode.com/2020/day/13)|-|-|
 |[14](https://adventofcode.com/2020/day/14)|-|-|
 |[15](https://adventofcode.com/2020/day/15)|-|-|
diff --git a/day12/main.py b/day12/main.py
@@ -0,0 +1,48 @@
+from parse import search
+
+with open("input.txt") as f:
+    code = [search("{}{:d}", x).fixed for x in f]
+
+posx = 0
+posy = 0
+dirs = ["E", "S", "W", "N"]
+ptr = 0
+
+for d, n in code:
+    if   d == "N": posy += n
+    elif d == "S": posy -= n
+    elif d == "E": posx += n
+    elif d == "W": posx -= n
+    elif d == "L": ptr = (ptr - n // 90) % len(dirs)
+    elif d == "R": ptr = (ptr + n // 90) % len(dirs)
+    elif d == "F":
+        if   dirs[ptr] == "N": posy += n
+        elif dirs[ptr] == "S": posy -= n
+        elif dirs[ptr] == "E": posx += n
+        elif dirs[ptr] == "W": posx -= n
+    
+print(abs(posx)+abs(posy))
+
+wpx = 10
+wpy = 1
+posx = 0
+posy = 0
+
+for d, n in code:
+    if   d == "N": wpy += n
+    elif d == "S": wpy -= n
+    elif d == "E": wpx += n
+    elif d == "W": wpx -= n
+    elif d in ("R", "L") and n == 180:
+        wpx, wpy = -wpx, -wpy
+    elif d == "R":
+        if n == 90:    wpx, wpy =  wpy, -wpx
+        elif n == 270: wpx, wpy = -wpy,  wpx
+    elif d == "L":
+        if n == 90:    wpx, wpy = -wpy,  wpx
+        elif n == 270: wpx, wpy =  wpy, -wpx
+    elif d == "F":
+        posx += n * wpx
+        posy += n * wpy
+    
+print(abs(posx)+abs(posy))
