Print the result
- Algorithms course
- Intermediate
- Lesson 76/80
- 4 min
Print the reachable cities.
Print the result
In the final step we will print the BFS results. Combine all pieces: build_cities, add_neighbor and bfs_reachable.
This lesson uses all previous functions; the initial code chain is complete.
The output is the sorted list of reachable cities; deterministic and readable.
Project complete
This mini project combined the city graph, neighbor addition and BFS reachability.
In real applications similar structures are used in maps, routing and network analysis.
BFS is a fundamental tool for reachability; this project shows its practical use.
Practice Print the result
Write print_reachable(graph, start). Call bfs_reachable and print with print(). Output of print_reachable(build_cities(), "A"): ['A', 'B', 'C', 'D'].
Starter code
def build_cities():
# Define the city graph
return {"A": ["B", "C"], "B": ["A", "D"], "C": ["A", "D"], "D": ["B", "C"]}
def add_neighbor(graph, city, neighbor):
# Add neighbor
graph[city].append(neighbor)
return graph
def bfs_reachable(graph, start):
# Reachable cities
visited = set()
queue = [start]
while queue:
node = queue.pop(0)
if node not in visited:
visited.add(node)
for nb in graph[node]:
if nb not in visited:
queue.append(nb)
return sorted(visited)
def print_reachable(graph, start):
# Print resultSample solution
def build_cities():
# Define the city graph
return {"A": ["B", "C"], "B": ["A", "D"], "C": ["A", "D"], "D": ["B", "C"]}
def add_neighbor(graph, city, neighbor):
# Add neighbor
graph[city].append(neighbor)
return graph
def bfs_reachable(graph, start):
# Reachable cities
visited = set()
queue = [start]
while queue:
node = queue.pop(0)
if node not in visited:
visited.add(node)
for nb in graph[node]:
if nb not in visited:
queue.append(nb)
return sorted(visited)
def print_reachable(graph, start):
# Print result
reachable = bfs_reachable(graph, start)
print(reachable)
print_reachable(build_cities(), "A")Expected output
['A', 'B', 'C', 'D']
Questions and answers
Review the lesson questions together with their answers. To test yourself, solve the lesson interactively.
1 Print the result: match the terms
| Term | Meaning |
|---|---|
print |
|
reachable |
Reachable |
sorted |
Sorted |
BFS |
Discovery |
2 Which structure was NOT used in this project?
- Visited set
- Graph
- Queue
- Heap Correct answer
Explanation: Heap.
3 Print
print(____)print(reachable)Explanation: reachable is right.