first

1 files changed, 39 insertions, 0 deletions

diff --git a/2023/24/solve.py b/2023/24/solve.py
new file mode 100644
index 0000000..c765c51
--- /dev/null
+++ b/2023/24/solve.py
@@ -0,0 +1,39 @@
+import numpy as np
+
+L = [
+    [[int(x) for x in b.strip().split(", ")] for b in l.split(" @ ")]
+    for l in open("input").readlines()
+]
+
+
+def collision(x1, y1, vx1, vy1, x2, y2, vx2, vy2):
+    a1 = np.array([x1, y1]).T
+    v1 = np.array([vx1, vy1]).T
+    a2 = np.array([x2, y2]).T
+    v2 = np.array([vx2, vy2]).T
+    sect, _, rank, *rst = np.linalg.lstsq(
+        np.array([v1, v2]).T, a2 - a1, rcond=None
+    )
+    if rank == 2:
+        return a1 + v1 * sect[0]
+    return np.array([-1, -1])
+
+
+res = 0
+# MIN = 7
+# MAX = 27
+MIN = 200000000000000
+MAX = 400000000000000
+for i, ((x1, y1, z1), (vx1, vy1, vz1)) in enumerate(L):
+    for j, ((x2, y2, z2), (vx2, vy2, vz2)) in enumerate(L[i + 1 :]):
+        x, y = collision(x1, y1, vx1, vy1, x2, y2, vx2, vy2)
+        res += (
+            MIN <= x <= MAX
+            and MIN <= y <= MAX
+            and (x - x1) * vx1 >= 0
+            and (y - y1) * vy1 >= 0
+            and (x - x2) * vx2 >= 0
+            and (y - y2) * vy2 >= 0
+        )
+
+print(res)