diff --git a/2018/07/input.txt b/2018/07/input.txt
new file mode 100644
index 0000000..6acbcdd
--- /dev/null
+++ b/2018/07/input.txt
@@ -0,0 +1,101 @@
+Step U must be finished before step A can begin.
+Step F must be finished before step Z can begin.
+Step B must be finished before step J can begin.
+Step O must be finished before step R can begin.
+Step H must be finished before step S can begin.
+Step T must be finished before step R can begin.
+Step L must be finished before step W can begin.
+Step M must be finished before step I can begin.
+Step Q must be finished before step K can begin.
+Step Z must be finished before step V can begin.
+Step C must be finished before step E can begin.
+Step W must be finished before step I can begin.
+Step K must be finished before step S can begin.
+Step I must be finished before step Y can begin.
+Step P must be finished before step V can begin.
+Step V must be finished before step X can begin.
+Step R must be finished before step E can begin.
+Step N must be finished before step E can begin.
+Step X must be finished before step J can begin.
+Step A must be finished before step J can begin.
+Step S must be finished before step G can begin.
+Step J must be finished before step E can begin.
+Step Y must be finished before step E can begin.
+Step D must be finished before step G can begin.
+Step E must be finished before step G can begin.
+Step K must be finished before step N can begin.
+Step B must be finished before step I can begin.
+Step X must be finished before step S can begin.
+Step V must be finished before step S can begin.
+Step U must be finished before step L can begin.
+Step N must be finished before step G can begin.
+Step O must be finished before step L can begin.
+Step X must be finished before step E can begin.
+Step V must be finished before step E can begin.
+Step Y must be finished before step G can begin.
+Step A must be finished before step Y can begin.
+Step M must be finished before step E can begin.
+Step F must be finished before step Q can begin.
+Step F must be finished before step X can begin.
+Step L must be finished before step C can begin.
+Step T must be finished before step L can begin.
+Step B must be finished before step C can begin.
+Step Q must be finished before step N can begin.
+Step T must be finished before step G can begin.
+Step R must be finished before step D can begin.
+Step I must be finished before step A can begin.
+Step B must be finished before step M can begin.
+Step H must be finished before step A can begin.
+Step F must be finished before step K can begin.
+Step U must be finished before step F can begin.
+Step R must be finished before step A can begin.
+Step J must be finished before step D can begin.
+Step V must be finished before step Y can begin.
+Step F must be finished before step J can begin.
+Step C must be finished before step K can begin.
+Step M must be finished before step C can begin.
+Step F must be finished before step E can begin.
+Step I must be finished before step E can begin.
+Step T must be finished before step A can begin.
+Step J must be finished before step Y can begin.
+Step R must be finished before step X can begin.
+Step W must be finished before step S can begin.
+Step V must be finished before step R can begin.
+Step U must be finished before step V can begin.
+Step C must be finished before step V can begin.
+Step F must be finished before step Y can begin.
+Step R must be finished before step G can begin.
+Step W must be finished before step N can begin.
+Step H must be finished before step N can begin.
+Step H must be finished before step Y can begin.
+Step B must be finished before step W can begin.
+Step M must be finished before step Z can begin.
+Step X must be finished before step A can begin.
+Step A must be finished before step G can begin.
+Step N must be finished before step A can begin.
+Step H must be finished before step J can begin.
+Step B must be finished before step O can begin.
+Step W must be finished before step A can begin.
+Step P must be finished before step N can begin.
+Step Z must be finished before step G can begin.
+Step W must be finished before step D can begin.
+Step D must be finished before step E can begin.
+Step W must be finished before step J can begin.
+Step N must be finished before step D can begin.
+Step C must be finished before step J can begin.
+Step B must be finished before step Y can begin.
+Step F must be finished before step P can begin.
+Step L must be finished before step P can begin.
+Step X must be finished before step G can begin.
+Step R must be finished before step Y can begin.
+Step K must be finished before step A can begin.
+Step M must be finished before step Y can begin.
+Step W must be finished before step Y can begin.
+Step F must be finished before step I can begin.
+Step L must be finished before step X can begin.
+Step R must be finished before step J can begin.
+Step V must be finished before step J can begin.
+Step V must be finished before step D can begin.
+Step H must be finished before step C can begin.
+Step O must be finished before step G can begin.
+Step P must be finished before step R can begin.
diff --git a/2018/07/solve.py b/2018/07/solve.py
new file mode 100644
index 0000000..9f685bc
--- /dev/null
+++ b/2018/07/solve.py
@@ -0,0 +1,115 @@
+import re
+import sys
+
+# PART 1
+
+STEP_RE = r"Step (\S+) must be finished before step (\S+) can begin.\n"
+
+def load_steps(filename):
+	steps = {}
+	with open(filename, "r") as f:
+		for line in f:
+			match = re.fullmatch(STEP_RE, line)
+			step, before = match.groups()
+			steps[step] = steps.get(step, set()) | {before}
+
+	return steps
+
+def reverse_steps(steps):
+	reverse = {}
+	for step, befores in steps.items():
+		# Make sure that step exists in reverse
+		reverse[step] = reverse.get(step, set())
+
+		for before in befores:
+			reverse[before] = reverse.get(before, set()) | {step}
+
+	return reverse
+
+def duration_of(step):
+	return ord(step) - ord("A") + 61
+
+class Tree:
+	def __init__(self, steps, workers=1):
+		self.workers = {i: None for i in range(workers)}
+		self.steps = reverse_steps(steps) # Warning: Steps are reversed in Trees.
+		self.result = []
+		self.duration = 0
+
+	def working(self):
+		return {worker: work for worker, work in self.workers.items() if work is not None}
+
+	def find_free(self):
+		return {step for step, afters in self.steps.items() if len(afters) == 0}
+
+	def find_working(self):
+		return {step for (step, _) in self.working().values()}
+
+	def find_available(self):
+		return self.find_free() - self.find_working()
+
+	def remove_step(self, step):
+		try:
+			del self.steps[step]
+		except KeyError:
+			pass
+
+		for s in self.steps.values():
+			try:
+				s.remove(step)
+			except KeyError:
+				pass
+
+	def update_workers(self):
+		min_duration = min(duration for (_, duration) in self.working().values())
+		self.duration += min_duration
+
+		finished_steps = set()
+
+		# Subtract min_duration from all workers
+		for w, s in self.workers.items():
+			if s is not None:
+				step, duration = s
+				duration -= min_duration
+
+				if duration <= 0:
+					finished_steps.add(step)
+					self.remove_step(step)
+					self.workers[w] = None
+				else:
+					self.workers[w] = (step, duration)
+
+		self.result += list(finished_steps)
+
+	def distribute_jobs(self):
+		available = list(reversed(sorted(self.find_available())))
+
+		for w, s in self.workers.items():
+			if not available:
+				break
+
+			if s is None:
+				step = available.pop()
+				duration = duration_of(step)
+				self.workers[w] = (step, duration)
+
+	def run(self):
+		while self.steps:
+			self.distribute_jobs()
+			self.update_workers()
+
+def main(filename):
+	print(f"Solutions for {filename}")
+	steps = load_steps(filename)
+	tree = Tree(steps, workers=1)
+	tree.run()
+	sequence = "".join(tree.result)
+	print(f"Part 1: {sequence}")
+	tree = Tree(steps, workers=5)
+	tree.run()
+	duration = tree.duration
+	print(f"Part 2: {duration}")
+
+if __name__ == "__main__":
+	for filename in sys.argv[1:]:
+		main(filename)
diff --git a/2018/07/test_input.txt b/2018/07/test_input.txt
new file mode 100644
index 0000000..9ab25bf
--- /dev/null
+++ b/2018/07/test_input.txt
@@ -0,0 +1,7 @@
+Step C must be finished before step A can begin.
+Step C must be finished before step F can begin.
+Step A must be finished before step B can begin.
+Step A must be finished before step D can begin.
+Step B must be finished before step E can begin.
+Step D must be finished before step E can begin.
+Step F must be finished before step E can begin.