コード例 #1
0
        """Find the group containing p and return the position of its leader.
        """
        if p._parent != p:
            # overwrite pos._parent after recursion
            p._parent = self.find(p._parent)
        return p._parent

    def union(self, p, q):
        """Merges the groups containing elements p and q."""
        a = self.find(p)
        b = self.find(q)
        if a is not b:
            if a._size > b._size:
                b._parent = a
                a._size += b._size
            else:
                a._parent = b
                b._size += a._size


if __name__ == "__main__":
    from graph_examples import figure_14_15 as example
    graph = example()
    edges = MST_PrimJarnik(graph)
    for edge in edges:
        print(str(edge))
    print("=" * 20)
    edges = MST_Kruskal(graph)
    for edge in edges:
        print(str(edge))
コード例 #2
0
ファイル: mst.py プロジェクト: storypku/tlpi
    def find(self, p):
        """Find the group containing p and return the position of its leader.
        """
        if p._parent != p:
            # overwrite pos._parent after recursion
            p._parent = self.find(p._parent)
        return p._parent

    def union(self, p, q):
        """Merges the groups containing elements p and q."""
        a = self.find(p)
        b = self.find(q)
        if a is not b:
            if a._size > b._size:
                b._parent = a
                a._size += b._size
            else:
                a._parent = b
                b._size += a._size

if __name__ == "__main__":
    from graph_examples import figure_14_15 as example
    graph = example()
    edges = MST_PrimJarnik(graph)
    for edge in edges:
        print(str(edge))
    print("="*20)
    edges = MST_Kruskal(graph)
    for edge in edges:
        print(str(edge))
コード例 #3
0
ファイル: bfs_incomplete.py プロジェクト: nsnider7/CSE331Repo
                    discovered[
                        v] = e  #e is the tree edge that is discovered in v
                    next_level.append(
                        v)  #v will be further considered in next pass
        level = next_level


def BFS_complete(g):
    """Perform BFS for entire graph and return forest as a dictionary.

  Result maps each vertex v to the edge that was used to discover it.
  (vertices that are roots of a BFS tree are mapped to None).
  """
    forest = {}
    for u in g.vertices():
        if u not in forest:
            forest[u] = None  #u will the root of our tree
            BFS(g, u, forest)
    return forest


if __name__ == '__main__':
    #from graph_examples import figure_14_11 as example
    from graph_examples import figure_14_9_smaller as example
    #from graph_examples import figure_14_12_smaller as example
    g = example()
    print("Number of vertices is", g.vertex_count())
    print("Number of edges is", g.edge_count())
    bfs = BFS_complete(g)
    print("BFS", [str(v) for v in bfs])
from copy import deepcopy


def floyd_warshall(g):
    """Return a new graph that is the transitive closure of g."""
    closure = deepcopy(g)  # imported from copy module
    verts = list(closure.vertices())  # make indexable list
    n = len(verts)
    for k in range(n):
        for i in range(n):
            # verify that edge (i,k) exists in the partial closure
            if i != k and closure.get_edge(verts[i], verts[k]) is not None:
                for j in range(n):
                    # verify that edge (k,j) exists in the partial closure
                    if i != j != k and closure.get_edge(verts[k], verts[j]) is not None:
                        # if (i,j) not yet included, add it to the closure
                        if closure.get_edge(verts[i], verts[j]) is None:
                            closure.insert_edge(verts[i], verts[j])
    return closure


if __name__ == '__main__':
    from graph_examples import figure_14_11 as example

    g = example()
    print("Number of vertices is", g.vertex_count())
    print("Number of edges is", g.edge_count())
    closure = floyd_warshall(g)
    print("Number of edges in closure is", closure.edge_count())