Day 12

2020/day12.py

@@ -0,0 +1,47 @@
+import sys
+
+
+def main():
+    codes = [(line[0], int(line.rstrip()[1:])) for line in sys.stdin]
+
+    # Part 1
+    x, y = 0, 0
+    dofs = [(1, 0), (0, -1), (-1, 0), (0, 1)]  # E S W N
+    dmap = {di: do for di, do in zip("ESWN", dofs)}
+    f = 0
+    for ci, cv in codes:
+        if (dd := dmap.get(ci)):
+            dx, dy = dd
+            x, y = x + dx * cv, y + dy * cv
+        elif ci in "LR":
+            r = cv // 90
+            f = (f - r if ci == "L" else f + r) % 4
+        else:  # F
+            dx, dy = dofs[f]
+            x, y = x + dx * cv, y + dy * cv
+    print("Manhattan distance:", abs(x) + abs(y))
+
+    # Part 2
+    x, y = 0, 0
+    wx, wy = 10, 1
+    for ci, cv in codes:
+        if (dd := dmap.get(ci)):
+            dx, dy = dd
+            wx, wy = wx + dx * cv, wy + dy * cv
+        elif ci in "LR":  # what are matrices
+            dx, dy = wx - x, wy - y
+            if (ci, cv) in (("R", 90), ("L", 270)):
+                wx, wy = x + dy, y - dx
+            elif (ci, cv) in (("R", 270), ("L", 90)):
+                wx, wy = x - dy, y + dx
+            else:  # 180°
+                wx, wy = x - dx, y - dy
+        else:  # F
+            dx, dy = wx - x, wy - y
+            x, y = x + dx * cv, y + dy * cv
+            wx, wy = x + dx, y + dy
+    print("Manhattan distance part 2:", abs(x) + abs(y))
+
+
+if __name__ == "__main__":
+    main()