Module « scipy.sparse.csgraph »

Fonction depth_first_order - module scipy.sparse.csgraph

Signature de la fonction depth_first_order

Description

depth_first_order.__doc__

    depth_first_order(csgraph, i_start, directed=True, return_predecessors=True)

    Return a depth-first ordering starting with specified node.

    Note that a depth-first order is not unique.  Furthermore, for graphs
    with cycles, the tree generated by a depth-first search is not
    unique either.

    .. versionadded:: 0.11.0

    Parameters
    ----------
    csgraph : array_like or sparse matrix
        The N x N compressed sparse graph.  The input csgraph will be
        converted to csr format for the calculation.
    i_start : int
        The index of starting node.
    directed : bool, optional
        If True (default), then operate on a directed graph: only
        move from point i to point j along paths csgraph[i, j].
        If False, then find the shortest path on an undirected graph: the
        algorithm can progress from point i to j along csgraph[i, j] or
        csgraph[j, i].
    return_predecessors : bool, optional
        If True (default), then return the predecesor array (see below).

    Returns
    -------
    node_array : ndarray, one dimension
        The depth-first list of nodes, starting with specified node.  The
        length of node_array is the number of nodes reachable from the
        specified node.
    predecessors : ndarray, one dimension
        Returned only if return_predecessors is True.
        The length-N list of predecessors of each node in a depth-first
        tree.  If node i is in the tree, then its parent is given by
        predecessors[i]. If node i is not in the tree (and for the parent
        node) then predecessors[i] = -9999.

    Examples
    --------
    >>> from scipy.sparse import csr_matrix
    >>> from scipy.sparse.csgraph import depth_first_order

    >>> graph = [
    ... [0, 1 , 2, 0],
    ... [0, 0, 0, 1],
    ... [2, 0, 0, 3],
    ... [0, 0, 0, 0]
    ... ]
    >>> graph = csr_matrix(graph)
    >>> print(graph)
      (0, 1)	1
      (0, 2)	2
      (1, 3)	1
      (2, 0)	2
      (2, 3)	3

    >>> depth_first_order(graph,0)
    (array([0, 1, 3, 2], dtype=int32), array([-9999,     0,     0,     1], dtype=int32))