add initial day12 solution

1 files changed, 39 insertions, 0 deletions

diff --git a/execs/Day12.hs b/execs/Day12.hs
new file mode 100644
index 0000000..72e0124
--- /dev/null
+++ b/execs/Day12.hs
@@ -0,0 +1,39 @@
+module Main where
+
+parseLine s = (head s, read (tail s) :: Float)
+
+moves ls = sum $ map (round . abs) [fx, fy]
+    where (fx, fy, _) = foldl fn (0.0, 0.0, 0.0) ls
+          fn (x, y, rot) ('N', v) = (x, y + v, rot)
+          fn (x, y, rot) ('E', v) = (x + v, y, rot)
+          fn (x, y, rot) ('W', v) = (x - v, y, rot)
+          fn (x, y, rot) ('S', v) = (x, y - v, rot)
+          fn (x, y, rot) ('R', v) = (x, y, rot - v)
+          fn (x, y, rot) ('L', v) = (x, y, rot + v)
+          fn (x, y, rot) ('F', v) = (nx, ny, rot)
+              where nx = x + v * cos (pi * rot / 180)
+                    ny = y + v*sin (pi * rot / 180)
+
+rotate (x, y) t = (nx, ny)
+    where nx = x*cos(pi*t/180) - y*sin(pi*t/180)
+          ny = x*sin(pi*t/180) + y*cos(pi*t/180)
+
+waypoint (sx, sy) ls = sum $ map (round . abs) [fx, fy]
+    where (fx, fy, _, _) = foldl fn (0.0, 0.0, sx, sy) ls
+          fn (x, y, wx, wy) ('N', v) = (x, y, wx, wy+v)
+          fn (x, y, wx, wy) ('E', v) = (x, y, wx+v, wy)
+          fn (x, y, wx, wy) ('W', v) = (x, y, wx-v, wy)
+          fn (x, y, wx, wy) ('S', v) = (x, y, wx, wy-v)
+          fn (x, y, wx, wy) ('R', v) = (x, y, nwx, nwy)
+              where p = negate v
+                    (nwx, nwy) = rotate (wx, wy) p
+          fn (x, y, wx, wy) ('L', v) = (x, y, nwx, nwy)
+              where (nwx, nwy) = rotate (wx, wy) v
+          fn (x, y, wx, wy) ('F', v) = (x+v*wx, y+v*wy, wx, wy)
+
+
+main :: IO ()
+main = do
+    n <- map parseLine . lines <$> readFile "input/12"
+    print $ moves n
+    print $ waypoint (10.0, 1.0) n