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68 lines
2.1 KiB
Python
68 lines
2.1 KiB
Python
"""
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* Author: Manuel Di Lullo (https://github.com/manueldilullo)
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* Description: Random graphs generator.
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Uses graphs represented with an adjacency list.
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URL: https://en.wikipedia.org/wiki/Random_graph
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"""
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import random
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def random_graph(
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vertices_number: int, probability: float, directed: bool = False
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) -> dict:
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"""
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Generate a random graph
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@input: vertices_number (number of vertices),
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probability (probability that a generic edge (u,v) exists),
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directed (if True: graph will be a directed graph,
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otherwise it will be an undirected graph)
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@examples:
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>>> random.seed(1)
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>>> random_graph(4, 0.5)
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{0: [1], 1: [0, 2, 3], 2: [1, 3], 3: [1, 2]}
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>>> random.seed(1)
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>>> random_graph(4, 0.5, True)
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{0: [1], 1: [2, 3], 2: [3], 3: []}
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"""
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graph: dict = {i: [] for i in range(vertices_number)}
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# if probability is greater or equal than 1, then generate a complete graph
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if probability >= 1:
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return complete_graph(vertices_number)
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# if probability is lower or equal than 0, then return a graph without edges
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if probability <= 0:
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return graph
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# for each couple of nodes, add an edge from u to v
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# if the number randomly generated is greater than probability probability
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for i in range(vertices_number):
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for j in range(i + 1, vertices_number):
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if random.random() < probability:
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graph[i].append(j)
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if not directed:
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# if the graph is undirected, add an edge in from j to i, either
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graph[j].append(i)
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return graph
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def complete_graph(vertices_number: int) -> dict:
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"""
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Generate a complete graph with vertices_number vertices.
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@input: vertices_number (number of vertices),
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directed (False if the graph is undirected, True otherwise)
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@example:
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>>> complete_graph(3)
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{0: [1, 2], 1: [0, 2], 2: [0, 1]}
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"""
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return {
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i: [j for j in range(vertices_number) if i != j] for i in range(vertices_number)
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}
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if __name__ == "__main__":
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import doctest
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doctest.testmod()
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