scipy.sparse.csgraph.breadth_first_order(csgraph, i_start, directed=True, return_predecessors=True)

Return a breadth-first ordering starting with specified node.

Note that a breadth-first order is not unique, but the tree which it generates is unique.

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 breadth-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 breadth-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.

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