structure.py 文件源码

def make_tree(edges):
    """Constructs a tree graph from a set of (vertex,vertex) pairs.

    Args:
        edges: A list or set of unordered (vertex, vertex) pairs.

    Returns: A tuple with elements:
        V: Number of vertices.
        E: Number of edges.
        grid: a 3 x E grid of (edge, vertex, vertex) triples.
    """
    assert all(isinstance(edge, tuple) for edge in edges)
    edges = [tuple(sorted(edge)) for edge in edges]
    edges.sort()
    E = len(edges)
    grid = np.zeros([3, E], np.int32)
    for e, (v1, v2) in enumerate(edges):
        grid[:, e] = [e, v1, v2]
    return grid