49 lines
999 B
Python
49 lines
999 B
Python
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from collections import deque
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from heapq import heappush, heappop
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from fixtures import weighted_graph
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def put(t, x, xs):
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if t == 'stack':
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return xs.append(x)
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if t == 'queue':
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return xs.append(x)
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if t == 'priority':
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return heappush(xs, x)
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def pop(t, xs):
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if t == 'stack':
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return xs.pop()
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if t == 'queue':
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return xs.popleft()
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if t == 'priority':
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return heappop(xs)
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# shortest_path :: Vertex -> Vertex -> Graph -> [Vertex]
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def shortest_path(a, b, g):
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"""Returns the shortest path from vertex a to vertex b in graph g."""
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t = 'priority'
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xs = []
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seen = set()
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# Map(Weight, [Vertex])
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m = {}
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put(t, (0, [a], a), xs)
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while xs:
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w0, path, v = pop(t, xs)
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seen.add(v)
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if v == b:
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m[w0] = path
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for w1, x in g.get(v):
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if x not in seen:
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put(t, (w0 + w1, path + [x], x), xs)
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return m
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print(shortest_path('a', 'f', graph_a))
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