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Fix RuntimeError in bipartite-check DFS/BFS and clean up doctests #12814

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Fix RuntimeError in bipartite-check DFS/BFS and clean up doctests #12814

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b008c3b
Fix `RuntimeError` in bipartite-check DFS/BFS and clean up doctests
odiomarcelino Jun 29, 2025
7bac59d
Fix RuntimeError in bipartite-check DFS/BFS and clean up doctests
mohiuddin-khan-shiam Jun 29, 2025
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16 changes: 5 additions & 11 deletions graphs/check_bipatrite.py
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Original file line number Diff line number Diff line change
Expand Up @@ -16,11 +16,8 @@ def is_bipartite_dfs(graph: defaultdict[int, list[int]]) -> bool:

Examples:

>>> # FIXME: This test should pass.
>>> is_bipartite_dfs(defaultdict(list, {0: [1, 2], 1: [0, 3], 2: [0, 4]}))
Traceback (most recent call last):
...
RuntimeError: dictionary changed size during iteration
True
>>> is_bipartite_dfs(defaultdict(list, {0: [1, 2], 1: [0, 3], 2: [0, 1]}))
False
>>> is_bipartite_dfs({})
Expand Down Expand Up @@ -86,7 +83,7 @@ def depth_first_search(node: int, color: int) -> bool:
return visited[node] == color

visited: defaultdict[int, int] = defaultdict(lambda: -1)
for node in graph:
for node in list(graph):
if visited[node] == -1 and not depth_first_search(node, 0):
return False
return True
Expand All @@ -107,11 +104,8 @@ def is_bipartite_bfs(graph: defaultdict[int, list[int]]) -> bool:

Examples:

>>> # FIXME: This test should pass.
>>> is_bipartite_bfs(defaultdict(list, {0: [1, 2], 1: [0, 3], 2: [0, 4]}))
Traceback (most recent call last):
...
RuntimeError: dictionary changed size during iteration
True
>>> is_bipartite_bfs(defaultdict(list, {0: [1, 2], 1: [0, 2], 2: [0, 1]}))
False
>>> is_bipartite_bfs({})
Expand Down Expand Up @@ -157,7 +151,7 @@ def is_bipartite_bfs(graph: defaultdict[int, list[int]]) -> bool:
KeyError: 'b'
"""
visited: defaultdict[int, int] = defaultdict(lambda: -1)
for node in graph:
for node in list(graph):
if visited[node] == -1:
queue: deque[int] = deque()
queue.append(node)
Expand All @@ -173,7 +167,7 @@ def is_bipartite_bfs(graph: defaultdict[int, list[int]]) -> bool:
return True


if __name__ == "__main":
if __name__ == "__main__":
import doctest

result = doctest.testmod()
Expand Down
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