1 files changed, 30 insertions, 0 deletions
diff --git a/2015/19/puzzle-1.py b/2015/19/puzzle-1.py
new file mode 100755
index 0000000..8527ca0
--- /dev/null
+++ b/2015/19/puzzle-1.py
@@ -0,0 +1,30 @@
+#!/usr/bin/env python3
+
+import re
+
+def main() -> None:
+	replacements: dict[str, str] = {}
+	with open("input", "r", encoding="utf-8") as f:
+		for line in f.readlines():
+			line = line.strip()
+			if line != "":
+				parts = line.split(" => ")
+				if len(parts) == 2:
+					while parts[0] in replacements:
+						parts[0] += "_"
+					replacements[parts[0]] = parts[1]
+				else:
+					molecule = line
+
+	unique_molecules: set[str] = set()
+	for pattern in replacements:
+		trim_pattern = pattern.replace("_", "")
+		for match in re.finditer(trim_pattern, molecule):
+			before = molecule[:match.start()]
+			after = molecule[match.start():].replace(trim_pattern, replacements[pattern], 1)
+			unique_molecules.add(before + after)
+	
+	print(len(unique_molecules))
+
+if __name__ == "__main__":
+	main()