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* graphs/kruskal: add doctest & type hints this is a child of a previous PR #2443 its ancestor is #2128 * updating DIRECTORY.md * graphs/kruskal: fix max-line-length violation * fixup! Format Python code with psf/black push Co-authored-by: github-actions <${GITHUB_ACTOR}@users.noreply.github.com>
48 lines
1.4 KiB
Python
48 lines
1.4 KiB
Python
from typing import List, Tuple
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def kruskal(num_nodes: int, num_edges: int, edges: List[Tuple[int, int, int]]) -> int:
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"""
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>>> kruskal(4, 3, [(0, 1, 3), (1, 2, 5), (2, 3, 1)])
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[(2, 3, 1), (0, 1, 3), (1, 2, 5)]
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>>> kruskal(4, 5, [(0, 1, 3), (1, 2, 5), (2, 3, 1), (0, 2, 1), (0, 3, 2)])
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[(2, 3, 1), (0, 2, 1), (0, 1, 3)]
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>>> kruskal(4, 6, [(0, 1, 3), (1, 2, 5), (2, 3, 1), (0, 2, 1), (0, 3, 2),
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... (2, 1, 1)])
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[(2, 3, 1), (0, 2, 1), (2, 1, 1)]
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"""
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edges = sorted(edges, key=lambda edge: edge[2])
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parent = list(range(num_nodes))
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def find_parent(i):
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if i != parent[i]:
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parent[i] = find_parent(parent[i])
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return parent[i]
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minimum_spanning_tree_cost = 0
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minimum_spanning_tree = []
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for edge in edges:
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parent_a = find_parent(edge[0])
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parent_b = find_parent(edge[1])
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if parent_a != parent_b:
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minimum_spanning_tree_cost += edge[2]
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minimum_spanning_tree.append(edge)
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parent[parent_a] = parent_b
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return minimum_spanning_tree
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if __name__ == "__main__": # pragma: no cover
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num_nodes, num_edges = list(map(int, input().strip().split()))
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edges = []
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for _ in range(num_edges):
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node1, node2, cost = [int(x) for x in input().strip().split()]
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edges.append((node1, node2, cost))
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kruskal(num_nodes, num_edges, edges)
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