2025(07): inspired by Marit, a new, better function

2025/07/part2.py

@@ -52,10 +52,35 @@ def quantum_propagate(x, subdiagram):
 		print("Reached end of world!")
 	return 1
 
+def sninkogate(diagram):
+	ylen = len(diagram)
+
+	# Find start location
+	y0 = 0
+	x0, = np.where(diagram[y0] == "S")[0]
+
+	# Save worlds per column
+	I = np.zeros_like(diagram, dtype=int)
+
+	# Emit starting beam
+	I[y0 + 1, x0] = 1
+
+	for y in range(2, ylen):
+		for x in np.where((diagram[y] == "^")&(I[y - 1] > 0))[0]:
+			# NOTE: I do not ever check whether carets are on the boundary.
+			I[y, (x - 1, x + 1)] += I[y - 1, x]
+		for x in np.where((diagram[y] == ".")&(I[y - 1] > 0))[0]:
+			I[y, x] += I[y - 1, x]
+		if debug:
+			print_diagram(diagram)
+			print()
+	return I[-1].sum()
+
+
 if __name__ == "__main__":
 	test_diagram = load_diagram("testinput")
 
 	assert quantum_propagate_diagram(test_diagram) == 40
 
 	diagram = load_diagram("input")
-	print(quantum_propagate_diagram(diagram))
+	print(sninkogate(diagram))