from networkx.utils import reverse_cuthill_mckee_ordering
import networkx as nx


def test_reverse_cuthill_mckee():
    # example graph from
    # http://www.boost.org/doc/libs/1_37_0/libs/graph/example/cuthill_mckee_ordering.cpp
    G = nx.Graph([(0, 3), (0, 5), (1, 2), (1, 4), (1, 6), (1, 9), (2, 3),
                  (2, 4), (3, 5), (3, 8), (4, 6), (5, 6), (5, 7), (6, 7)])
    rcm = list(reverse_cuthill_mckee_ordering(G))
    assert rcm in [[0, 8, 5, 7, 3, 6, 2, 4, 1, 9],
                        [0, 8, 5, 7, 3, 6, 4, 2, 1, 9]]


def test_rcm_alternate_heuristic():
    # example from
    G = nx.Graph([(0, 0),
                  (0, 4),
                  (1, 1),
                  (1, 2),
                  (1, 5),
                  (1, 7),
                  (2, 2),
                  (2, 4),
                  (3, 3),
                  (3, 6),
                  (4, 4),
                  (5, 5),
                  (5, 7),
                  (6, 6),
                  (7, 7)])

    answers = [[6, 3, 5, 7, 1, 2, 4, 0], [6, 3, 7, 5, 1, 2, 4, 0],
               [7, 5, 1, 2, 4, 0, 6, 3]]

    def smallest_degree(G):
        deg, node = min((d, n) for n, d in G.degree())
        return node
    rcm = list(reverse_cuthill_mckee_ordering(G, heuristic=smallest_degree))
    assert rcm in answers
