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

Original file line number	Diff line number	Diff line change
		@@ -1,7 +1,7 @@
		from collections import defaultdict, deque


	def is_bipartite_dfs(graph: defaultdict[int, list[int]]) -> bool:
	def is_bipartite_dfs(graph: dict[int, list[int]]) -> bool:
		"""
		Check if a graph is bipartite using depth-first search (DFS).

Expand All		@@ -16,12 +16,9 @@ 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
	>>> is_bipartite_dfs(defaultdict(list, {0: [1, 2], 1: [0, 3], 2: [0, 1]}))
	>>> is_bipartite_dfs({0: [1, 2], 1: [0, 3], 2: [0, 4]})
	True
	>>> is_bipartite_dfs({0: [1, 2], 1: [0, 3], 2: [0, 1]})
		False
		>>> is_bipartite_dfs({})
		True
Expand All		@@ -34,36 +31,26 @@ def is_bipartite_dfs(graph: defaultdict[int, list[int]]) -> bool:
		>>> is_bipartite_dfs({0: [1, 3], 1: [0, 2], 2: [1, 3], 3: [0, 2], 4: [0]})
		False
		>>> is_bipartite_dfs({7: [1, 3], 1: [0, 2], 2: [1, 3], 3: [0, 2], 4: [0]})
	Traceback (most recent call last):
	...
	KeyError: 0
	False

		>>> # FIXME: This test should fails with KeyError: 4.
		>>> is_bipartite_dfs({0: [1, 3], 1: [0, 2], 2: [1, 3], 3: [0, 2], 9: [0]})
		False
		>>> is_bipartite_dfs({0: [-1, 3], 1: [0, -2]})
	Traceback (most recent call last):
	...
	KeyError: -1
	False
		>>> is_bipartite_dfs({-1: [0, 2], 0: [-1, 1], 1: [0, 2], 2: [-1, 1]})
		True
		>>> is_bipartite_dfs({0.9: [1, 3], 1: [0, 2], 2: [1, 3], 3: [0, 2]})
	Traceback (most recent call last):
	...
	KeyError: 0
	True

		>>> # FIXME: This test should fails with
		>>> # TypeError: list indices must be integers or...
		>>> is_bipartite_dfs({0: [1.0, 3.0], 1.0: [0, 2.0], 2.0: [1.0, 3.0], 3.0: [0, 2.0]})
		True
		>>> is_bipartite_dfs({"a": [1, 3], "b": [0, 2], "c": [1, 3], "d": [0, 2]})
	Traceback (most recent call last):
	...
	KeyError: 1
	True
		>>> is_bipartite_dfs({0: ["b", "d"], 1: ["a", "c"], 2: ["b", "d"], 3: ["a", "c"]})
	Traceback (most recent call last):
	...
	KeyError: 'b'
	True
		"""

		def depth_first_search(node: int, color: int) -> bool:
Expand All		@@ -80,6 +67,8 @@ def depth_first_search(node: int, color: int) -> bool:
		"""
		if visited[node] == -1:
		visited[node] = color
	if node not in graph:
	return True
		for neighbor in graph[node]:
		if not depth_first_search(neighbor, 1 - color):
		return False
Expand All		@@ -92,7 +81,7 @@ def depth_first_search(node: int, color: int) -> bool:
		return True


	def is_bipartite_bfs(graph: defaultdict[int, list[int]]) -> bool:
	def is_bipartite_bfs(graph: dict[int, list[int]]) -> bool:
		"""
		Check if a graph is bipartite using a breadth-first search (BFS).

Expand All		@@ -107,12 +96,9 @@ 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
	>>> is_bipartite_bfs(defaultdict(list, {0: [1, 2], 1: [0, 2], 2: [0, 1]}))
	>>> is_bipartite_bfs({0: [1, 2], 1: [0, 3], 2: [0, 4]})
	True
	>>> is_bipartite_bfs({0: [1, 2], 1: [0, 2], 2: [0, 1]})
		False
		>>> is_bipartite_bfs({})
		True
Expand All		@@ -125,36 +111,26 @@ def is_bipartite_bfs(graph: defaultdict[int, list[int]]) -> bool:
		>>> is_bipartite_bfs({0: [1, 3], 1: [0, 2], 2: [1, 3], 3: [0, 2], 4: [0]})
		False
		>>> is_bipartite_bfs({7: [1, 3], 1: [0, 2], 2: [1, 3], 3: [0, 2], 4: [0]})
	Traceback (most recent call last):
	...
	KeyError: 0
	False

		>>> # FIXME: This test should fails with KeyError: 4.
		>>> is_bipartite_bfs({0: [1, 3], 1: [0, 2], 2: [1, 3], 3: [0, 2], 9: [0]})
		False
		>>> is_bipartite_bfs({0: [-1, 3], 1: [0, -2]})
	Traceback (most recent call last):
	...
	KeyError: -1
	False
		>>> is_bipartite_bfs({-1: [0, 2], 0: [-1, 1], 1: [0, 2], 2: [-1, 1]})
		True
		>>> is_bipartite_bfs({0.9: [1, 3], 1: [0, 2], 2: [1, 3], 3: [0, 2]})
	Traceback (most recent call last):
	...
	KeyError: 0
	True

		>>> # FIXME: This test should fails with
		>>> # TypeError: list indices must be integers or...
		>>> is_bipartite_bfs({0: [1.0, 3.0], 1.0: [0, 2.0], 2.0: [1.0, 3.0], 3.0: [0, 2.0]})
		True
		>>> is_bipartite_bfs({"a": [1, 3], "b": [0, 2], "c": [1, 3], "d": [0, 2]})
	Traceback (most recent call last):
	...
	KeyError: 1
	True
		>>> is_bipartite_bfs({0: ["b", "d"], 1: ["a", "c"], 2: ["b", "d"], 3: ["a", "c"]})
	Traceback (most recent call last):
	...
	KeyError: 'b'
	True
		"""
		visited: defaultdict[int, int] = defaultdict(lambda: -1)
		for node in graph:
Expand All		@@ -164,6 +140,8 @@ def is_bipartite_bfs(graph: defaultdict[int, list[int]]) -> bool:
		visited[node] = 0
		while queue:
		curr_node = queue.popleft()
	if curr_node not in graph:
	continue
		for neighbor in graph[curr_node]:
		if visited[neighbor] == -1:
		visited[neighbor] = 1 - visited[curr_node]
Expand All		@@ -173,7 +151,7 @@ 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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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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