Solve 2017/09

2017/09/solve.py

@@ -0,0 +1,95 @@
+import sys
+
+# PART 1
+
+class Stream:
+	def __init__(self, string):
+		self.content = list(string)
+		self.content.reverse()
+
+	def peek(self):
+		return self.content[-1]
+
+	def pop(self):
+		return self.content.pop()
+
+def load_groups(filename):
+	groups = []
+	with open(filename, "r") as f:
+		for line in f:
+			stream = Stream(line[:-1])
+			group, garbage = parse_group(stream)
+			groups.append((group, garbage))
+	return groups
+
+def parse_group(stream):
+	assert stream.pop() == "{"
+
+	if stream.peek() == "}":
+		assert stream.pop() == "}"
+		return [], 0
+
+	groups = []
+	garbage = 0
+
+	while True:
+		# Determine which sub-parser to use
+		if stream.peek() == "{":
+			group, more_garbage = parse_group(stream)
+			groups.append(group)
+			garbage += more_garbage
+		elif stream.peek() == "<":
+			garbage += parse_garbage(stream)
+		else:
+			raise Exception("Incorrectly formatted input")
+
+		# Determine whether to stop parsing
+		if stream.peek() == "}":
+			break
+		elif stream.peek() == ",":
+			assert stream.pop() == ","
+		else:
+			raise Exception("Incorrectly formatted input")
+
+	assert stream.pop() == "}"
+	return groups, garbage
+
+def parse_garbage(stream):
+	assert stream.pop() == "<"
+
+	escaped = False
+	garbage = 0
+
+	while True:
+		if escaped:
+			stream.pop()
+			escaped = False
+		elif stream.peek() == "!":
+			assert stream.pop() == "!"
+			escaped = True
+		elif stream.peek() == ">":
+			break
+		else:
+			stream.pop()
+			garbage += 1
+
+	assert stream.pop() == ">"
+
+	return garbage
+
+def group_score(group, level=1):
+	return sum(group_score(subgroup, level + 1) for subgroup in group) + level
+
+# PART 2
+
+def main(filename):
+	print(f"Solutions for {filename}")
+	groups = load_groups(filename)
+	for group, garbage in groups:
+		score = group_score(group)
+		print(f"Part 1: {score}")
+		print(f"Part 2: {garbage}")
+
+if __name__ == "__main__":
+	for filename in sys.argv[1:]:
+		main(filename)