53 lines
1.3 KiB
Python
53 lines
1.3 KiB
Python
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"""
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==========================
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Traveling Salesman Problem
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==========================
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This is an example of a drawing solution of the traveling salesman problem
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The function is used to produce the solution is christofides,
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where given a set of nodes, it calculates the route of the nodes
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that the traveler has to follow in order to minimize the total cost.
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"""
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import matplotlib.pyplot as plt
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import networkx as nx
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import networkx.algorithms.approximation as nx_app
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import math
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G = nx.random_geometric_graph(20, radius=0.4, seed=3)
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pos = nx.get_node_attributes(G, "pos")
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# Depot should be at (0,0)
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pos[0] = (0.5, 0.5)
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H = G.copy()
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# Calculating the distances between the nodes as edge's weight.
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for i in range(len(pos)):
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for j in range(i + 1, len(pos)):
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dist = math.hypot(pos[i][0] - pos[j][0], pos[i][1] - pos[j][1])
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dist = dist
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G.add_edge(i, j, weight=dist)
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cycle = nx_app.christofides(G, weight="weight")
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edge_list = list(nx.utils.pairwise(cycle))
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# Draw closest edges on each node only
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nx.draw_networkx_edges(H, pos, edge_color="blue", width=0.5)
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# Draw the route
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nx.draw_networkx(
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G,
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pos,
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with_labels=True,
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edgelist=edge_list,
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edge_color="red",
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node_size=200,
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width=3,
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)
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print("The route of the traveller is:", cycle)
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plt.show()
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