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62 lines
1.5 KiB
Python
62 lines
1.5 KiB
Python
"""
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LeetCode 133. Clone Graph
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https://leetcode.com/problems/clone-graph/
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Given a reference of a node in a connected undirected graph.
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Return a deep copy (clone) of the graph.
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Each node in the graph contains a value (int) and a list (List[Node]) of its
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neighbors.
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"""
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class Node:
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def __init__(self, value=0, neighbors=None):
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self.value = value
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self.neighbors = neighbors if neighbors is not None else []
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def clone_graph(node: Node | None) -> Node | None:
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"""
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This function returns a clone of a connected undirected graph.
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>>> clone_graph(Node(1))
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Node(1)
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>>> clone_graph(Node(1, [Node(2)]))
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Node(1, [Node(2)])
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>>> clone_graph(None)
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None
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"""
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if not node:
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return None
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originals_to_clones = {} # map nodes to clones
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def create_clones(node: Node) -> None:
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"""
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This helper function populates the originals_to_clones map with
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the original nodes in the graph mapped to newly created clones.
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"""
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if node in originals_to_clones:
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return
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originals_to_clones[node] = Node(node.value)
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for neighbor in node.neighbors:
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create_clones(neighbor)
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create_clones(node)
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for original, clone in originals_to_clones.items():
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for neighbor in original.neighbors:
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cloned_neighbor = originals_to_clones[neighbor]
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clone.neighbors.append(cloned_neighbor)
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return originals_to_clones[node]
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if __name__ == "__main__":
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import doctest
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doctest.testmod()
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