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Fix mypy error and add more doctest on bfs_shortest_path #4512

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Jun 29, 2021
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Fix mypy error and add more doctest on bfs_shortest_path #4512

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24 changes: 14 additions & 10 deletions graphs/bfs_shortest_path.py
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Original file line number Diff line number Diff line change
Expand Up @@ -4,7 +4,7 @@
Manual test:
python bfs_shortest_path.py
"""
graph = {
demo_graph = {
"A": ["B", "C", "E"],
"B": ["A", "D", "E"],
"C": ["A", "F", "G"],
Expand All @@ -15,7 +15,7 @@
}


def bfs_shortest_path(graph: dict, start, goal) -> str:
def bfs_shortest_path(graph: dict, start, goal) -> list[str]:
"""Find shortest path between `start` and `goal` nodes.
Args:
graph (dict): node/list of neighboring nodes key/value pairs.
Expand All @@ -25,8 +25,12 @@ def bfs_shortest_path(graph: dict, start, goal) -> str:
Shortest path between `start` and `goal` nodes as a string of nodes.
'Not found' string if no path found.
Example:
>>> bfs_shortest_path(graph, "G", "D")
>>> bfs_shortest_path(demo_graph, "G", "D")
['G', 'C', 'A', 'B', 'D']
>>> bfs_shortest_path(demo_graph, "G", "G")
['G']
>>> bfs_shortest_path(demo_graph, "G", "Unknown")
[]
"""
# keep track of explored nodes
explored = set()
Expand All @@ -35,7 +39,7 @@ def bfs_shortest_path(graph: dict, start, goal) -> str:

# return path if start is goal
if start == goal:
return "That was easy! Start = goal"
return [start]

# keeps looping until all possible paths have been checked
while queue:
Expand All @@ -59,7 +63,7 @@ def bfs_shortest_path(graph: dict, start, goal) -> str:
explored.add(node)

# in case there's no path between the 2 nodes
return "So sorry, but a connecting path doesn't exist :("
return []


def bfs_shortest_path_distance(graph: dict, start, target) -> int:
Expand All @@ -72,11 +76,11 @@ def bfs_shortest_path_distance(graph: dict, start, target) -> int:
Number of edges in shortest path between `start` and `target` nodes.
-1 if no path exists.
Example:
>>> bfs_shortest_path_distance(graph, "G", "D")
>>> bfs_shortest_path_distance(demo_graph, "G", "D")
4
>>> bfs_shortest_path_distance(graph, "A", "A")
>>> bfs_shortest_path_distance(demo_graph, "A", "A")
0
>>> bfs_shortest_path_distance(graph, "A", "H")
>>> bfs_shortest_path_distance(demo_graph, "A", "Unknown")
-1
"""
if not graph or start not in graph or target not in graph:
Expand All @@ -102,5 +106,5 @@ def bfs_shortest_path_distance(graph: dict, start, target) -> int:


if __name__ == "__main__":
print(bfs_shortest_path(graph, "G", "D")) # returns ['G', 'C', 'A', 'B', 'D']
print(bfs_shortest_path_distance(graph, "G", "D")) # returns 4
print(bfs_shortest_path(demo_graph, "G", "D")) # returns ['G', 'C', 'A', 'B', 'D']
print(bfs_shortest_path_distance(demo_graph, "G", "D")) # returns 4