scipy.sparse.csgraph.

Return the tree generated by a breadth-first search

Note that a breadth-first tree from a specified node is unique.

Parameters:
csgrapharray_like or sparse matrix

The N x N matrix representing the compressed sparse graph. The input csgraph will be converted to csr format for the calculation.

i_startint

The index of starting node.

directedbool, 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].

Returns:
cstreecsr matrix

The N x N directed compressed-sparse representation of the breadth- first tree drawn from csgraph, starting at the specified node.

Notes

If multiple valid solutions are possible, output may vary with SciPy and Python version.

Examples

The following example shows the computation of a depth-first tree over a simple four-component graph, starting at node 0:

``` input graph          breadth first tree from (0)

(0)                         (0)
/   \                       /   \
3     8                     3     8
/       \                   /       \
(3)---5---(1)               (3)       (1)
\       /                           /
6     2                           2
\   /                           /
(2)                         (2)
```

In compressed sparse representation, the solution looks like this:

```>>> from scipy.sparse import csr_matrix