def test_add_weight_no_edge(self):
"""
Test addting the weight of an edge that does not exist.
"""
g = Graph()
g.add_node("A")
g.add_node("B")
with self.assertRaises(ValueError) as context:
g.add_weight("A", "B", 1.51)
self.assertIn("edge", str(context.exception))
def test_add_weight_invalid_start(self):
"""
Test addting the weight of an edge where the start node does not exist.
"""
g = Graph()
g.add_node("A")
g.add_node("B")
with self.assertRaises(ValueError) as context:
g.add_weight("C", "B", 20.00)
self.assertIn("start", str(context.exception))
def test_add_weight_invalid_end(self):
"""
Test addting the weight of an edge where the end node does not exist.
"""
g = Graph()
g.add_node("A")
g.add_node("B")
with self.assertRaises(ValueError) as context:
g.add_weight("A", "C", 44.43)
self.assertIn("end", str(context.exception))
def test_add_weight(self):
"""
Test updating the weight of an edge between two nodes.
"""
correct = "{'A': {'B': 3.14}, 'B': {}}"
g = Graph()
g.add_node("A")
g.add_node("B")
g.add_edge("A", "B")
g.add_weight("A", "B", 3.14)
self.assertEqual(str(g), correct)
class EvenSplit():
"""
The EvenSplit class contains the code which handles adding people,
transactions, and reducing the graph into the minimum number of
transactions.
"""
def __init__(self):
"""
Construct a new EvenSplit instance.
"""
self.graph = Graph()
def __str__(self):
"""
Return a string form of the EvenSplit object. This is the same as
using the internal graph's __str__ function.
"""
return str(self.graph)
def __repr__(self):
"""
Return a human-readable string form of the EvenSplit object. This is
the same as using the internal graph's __repr__ function.
"""
return repr(self.graph)
def add_person(self, name: str):
"""
Add a new person to the EvenSplit object. This adds a new node for the
given name and connects it to all other nodes within the graph,
excluding itself.
"""
if name is None:
raise ValueError("Name cannot be None!")
self.graph.add_node(name)
for person in self.graph:
if person != name:
self.graph.add_edge(name, person)
self.graph.add_edge(person, name)
def add_transaction(self, name: str, amount: float):
"""
Add a transaction and evenly split the amount across all people.
"""
split_amount = amount / self.count()
for person in self.graph:
if person != name:
self.graph.add_weight(person, name, split_amount)
def count(self):
"""
Return the number of people in the graph.
"""
return self.graph.size()
def read(self, i: IO[str] = stdin):
"""
Read in the people and their transactions and construct the graph
with the input.
"""
num_users = int(next(i))
for _ in range(num_users):
self.add_person(next(i).strip())
num_transactions = int(next(i))
for _ in range(num_transactions):
line = next(i).split()
self.add_transaction(line[0], float(line[1]))
def print(self, out: IO[str] = stdout):
"""
Print the state of the split as transactions from one
person to another.
"""
out.write("Here's how to get even:\n")
for person in self.graph:
for other in self.graph[person]:
amount = "${:,.2f}".format(self.graph[person][other])
out.write(person + " pays " + other + " " + amount + "\n")