Day 10 part 2

2019/day10.py

@@ -1,14 +1,24 @@
-import math
+from collections import defaultdict
+import time
 
 import numpy as np
 
 
 DIM = 40
 
+EX = [
+    ".#....#####...#..",
+    "##...##.#####..##",
+    "##...#...#.#####.",
+    "..#.....#...###..",
+    "..#.#.....#....##",
+]
+
 
 def main():
     with open("day10.txt", "rt") as input_file:
         amap = [line.rstrip() for line in input_file.readlines()]
+        # amap = [line.rstrip() for line in EX]
 
     asteroids = []
     for y, line in enumerate(amap):
@@ -24,27 +34,72 @@ def main():
         if vis > best_vis:
             best_vis, best_pos = vis, pos
     print(f"Best visibility is {best_vis} at {best_pos}.")
-    draw(asteroids, best_pos)
 
-def draw(asteroids, station_pos):
+    # Part 2
+    pos = best_pos
+    asteroids.remove(pos)
+    destroyed = 0
+    angles = defaultdict(list)
+    for a in asteroids:
+        angle = np.angle(np.complex(a[0] - pos[0], a[1] - pos[1]), deg=True)
+        angles[angle].append(a)
+    current_angle = -90.0
+    while asteroids:
+        print(f"Laser at {pos}.")
+        print(f"Current angle: {current_angle}.")
+        targets = angles[current_angle]
+        try:
+            next_angle = min([a for a in angles.keys() if a > current_angle]) 
+        except ValueError:
+            next_angle = -180.0
+        if not targets:
+            current_angle = next_angle
+            continue
+        print(f"Acquired targets {targets}.")
+        nearest_target = min(targets, key=lambda t: dist_idea(pos, t))
+        print(f"Nearest target: {nearest_target}.")
+
+        # Pew!
+        asteroids.remove(nearest_target)
+        targets.remove(nearest_target)
+
+        destroyed += 1
+        print(f"Destroyed {nearest_target} -- total of {destroyed} asteroids.")
+        if destroyed == 200:
+            print(f"Destroyed 200th asteroid at {nearest_target}.")
+            break
+
+        current_angle = next_angle
+
+        draw(asteroids, pos, [nearest_target])
+        time.sleep(0.2)
+
+    print(f"Answer: {100 * nearest_target[0] + nearest_target[1]}.")
+
+def draw(asteroids, station_pos, specials=[]):
     for y in range(DIM):
         print(str(y).zfill(2), end=" ")
         for x in range(DIM):
             if (x, y) == station_pos:
                 print("@", end="")
+            elif (x, y) in specials:
+                print("X", end="")
             elif (x, y) in asteroids:
                 print("█", end="")
             else:
                 print(" ", end="")
         print()
-    print("  " + "0123456789"*4)
+    print("   " + "0123456789"*4)
 
-def num_visible_asts(asts, ref):
-    asts = asts.copy()
-    asts.remove(ref)
-    angles = [np.angle(np.complex(ast[0] - ref[0], ast[1] - ref[1])) for ast in asts]
+def num_visible_asts(asteroids, ref):
+    asteroids = asteroids.copy()
+    asteroids.remove(ref)
+    angles = [np.angle(np.complex(a[0] - ref[0], a[1] - ref[1])) for a in asteroids]
     return len(set(angles))
 
+def dist_idea(a, b):
+    return (a[0] - b[0]) ** 2 + (a[1] - b[1]) ** 2
+
 
 if __name__ == "__main__":
     main()