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* [ADD] tests for check_bipartite_graph_bfs * linter fix? * linter fix * [ADD] more test cases check_bipartite_graph_bfs * doctest fixes. Forgot to add 'Traceback...' * [pre-commit.ci] auto fixes from pre-commit.com hooks for more information, see https://pre-commit.ci * missed a Traceback * Update check_bipartite_graph_bfs.py --------- Co-authored-by: pre-commit-ci[bot] <66853113+pre-commit-ci[bot]@users.noreply.github.com> Co-authored-by: Christian Clauss <cclauss@me.com>
93 lines
2.9 KiB
Python
93 lines
2.9 KiB
Python
# Check whether Graph is Bipartite or Not using BFS
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# A Bipartite Graph is a graph whose vertices can be divided into two independent sets,
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# U and V such that every edge (u, v) either connects a vertex from U to V or a vertex
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# from V to U. In other words, for every edge (u, v), either u belongs to U and v to V,
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# or u belongs to V and v to U. We can also say that there is no edge that connects
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# vertices of same set.
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from queue import Queue
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def check_bipartite(graph):
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"""
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>>> check_bipartite({})
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True
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>>> check_bipartite({0: [1, 3], 1: [0, 2], 2: [1, 3], 3: [0, 2]})
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True
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>>> check_bipartite({0: [1, 2, 3], 1: [0, 2], 2: [0, 1, 3], 3: [0, 2]})
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False
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>>> check_bipartite({0: [4], 1: [], 2: [4], 3: [4], 4: [0, 2, 3]})
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True
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>>> check_bipartite({0: [1, 3], 1: [0, 2], 2: [1, 3], 3: [0, 2], 4: [0]})
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False
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>>> check_bipartite({7: [1, 3], 1: [0, 2], 2: [1, 3], 3: [0, 2], 4: [0]})
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Traceback (most recent call last):
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...
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KeyError: 0
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>>> check_bipartite({0: [1, 3], 1: [0, 2], 2: [1, 3], 3: [0, 2], 9: [0]})
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Traceback (most recent call last):
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...
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KeyError: 4
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>>> check_bipartite({0: [-1, 3], 1: [0, -2]})
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Traceback (most recent call last):
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...
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IndexError: list index out of range
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>>> check_bipartite({-1: [0, 2], 0: [-1, 1], 1: [0, 2], 2: [-1, 1]})
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True
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>>> check_bipartite({0.9: [1, 3], 1: [0, 2], 2: [1, 3], 3: [0, 2]})
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Traceback (most recent call last):
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...
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KeyError: 0
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>>> check_bipartite({0: [1.0, 3.0], 1.0: [0, 2.0], 2.0: [1.0, 3.0], 3.0: [0, 2.0]})
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Traceback (most recent call last):
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...
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TypeError: list indices must be integers or slices, not float
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>>> check_bipartite({"a": [1, 3], "b": [0, 2], "c": [1, 3], "d": [0, 2]})
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Traceback (most recent call last):
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...
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KeyError: 0
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>>> check_bipartite({0: ["b", "d"], 1: ["a", "c"], 2: ["b", "d"], 3: ["a", "c"]})
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Traceback (most recent call last):
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...
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TypeError: list indices must be integers or slices, not str
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"""
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queue = Queue()
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visited = [False] * len(graph)
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color = [-1] * len(graph)
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def bfs():
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while not queue.empty():
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u = queue.get()
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visited[u] = True
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for neighbour in graph[u]:
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if neighbour == u:
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return False
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if color[neighbour] == -1:
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color[neighbour] = 1 - color[u]
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queue.put(neighbour)
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elif color[neighbour] == color[u]:
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return False
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return True
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for i in range(len(graph)):
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if not visited[i]:
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queue.put(i)
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color[i] = 0
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if bfs() is False:
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return False
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return True
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if __name__ == "__main__":
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# Adjacency List of graph
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print(check_bipartite({0: [1, 3], 1: [0, 2], 2: [1, 3], 3: [0, 2]}))
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import doctest
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doctest.testmod()
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