[2023/24] p1 solved

2023/24/example

@@ -0,0 +1,5 @@
+19, 13, 30 @ -2,  1, -2
+18, 19, 22 @ -1, -1, -2
+20, 25, 34 @ -2, -2, -4
+12, 31, 28 @ -1, -2, -1
+20, 19, 15 @  1, -5, -3

2023/24/script.py

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+from GhostyUtils import aoc
+from GhostyUtils.vec2 import Vec2
+import math
+import itertools
+
+
+MIN = 200000000000000
+MAX = 400000000000000
+
+
+def ray_intersection(ray_a, ray_b):
+    a_pos, a_vel = ray_a
+    b_pos, b_vel = ray_b
+    dx = b_pos.x - a_pos.x
+    dy = b_pos.y - a_pos.y
+    det = b_vel.x * a_vel.y - b_vel.y * a_vel.x
+    if det == 0:
+        return False
+    u = (dy * b_vel.x - dx * b_vel.y) / det
+    v = (dy * a_vel.x - dx * a_vel.y) / det
+    p = a_pos + a_vel * u
+    return p, (u, v)
+
+
+if __name__ == "__main__":
+    hail = []
+    for hail_txt in aoc.read_lines():
+        pos, v = hail_txt.split(' @ ')
+        pos = Vec2(tuple(map(int, pos.split(', ')[:-1])))
+        v = Vec2(tuple(map(int, v.split(', ')[:-1])))
+        hail.append((pos, v))
+
+    collisions_in_area = 0
+    for t1, t2 in itertools.combinations(hail, 2):
+        print(f'Hailstone A: {t1[0]} @ {t1[1]}')
+        print(f'Hailstone B: {t2[0]} @ {t2[1]}')
+        result = ray_intersection(t1, t2)
+        if result:
+            p, (u, v) = result
+            if u < 0 and v < 0:
+                print("Hailstones' paths crossed in the past for both hailstones")
+            elif u < 0:
+                print("Hailstones' paths crossed in the past for hailstone A")
+            elif v < 0:
+                print("Hailstones' paths crossed in the past for hailstone B")
+            elif MIN <= p.x <= MAX and MIN <= p.y <= MAX:
+                collisions_in_area += 1
+                print(f"Hailstones' paths will cross inside the test area (at {p})")
+            else:
+                print(f"Hailstones' paths will cross outside the test area (at {p})")
+        else:
+            print("Hailstones' paths are parallel; they never intersect")
+        print()
+
+    print('p1:', collisions_in_area)