Has path (#952)

* Added has_path for PyGraph and PyDiGraph

* Fixed linting errors and added release notes

* Fixed doc type

* Fixed cargo fmt problem

* Fixed clippy problem

* Typo in release notes

* Apply suggestions from code review

* Remove whitespace

---------

Co-authored-by: Ivan Carvalho <[email protected]>

releasenotes/notes/has_path-1addf94c4d29d455.yaml

@@ -0,0 +1,21 @@
+---
+features:
+  - |
+    Added :func:`~rustworkx.has_path` which accepts as arguments a :class:`~rustworkx.PyGraph` or :class:`~rustworkx.PyDiGraph` and checks if there is a path from source to destination
+
+    .. jupyter-execute::
+    
+        from rustworkx import PyDiGraph, has_path
+
+        graph = PyDiGraph()
+        a = graph.add_node("A")
+        b = graph.add_node("B")
+        c = graph.add_node("C")
+        edge_list = [(a, b, 1), (b, c, 1)]
+        graph.add_edges_from(edge_list)
+
+        path_exists = has_path(graph, a, c)
+        assert(path_exists == True)
+
+        path_exists = has_path(graph, c, a)
+        assert(path_exists == False)

rustworkx/__init__.py

@@ -587,6 +587,39 @@ def _graph_dijkstra_shortest_path(graph, source, target=None, weight_fn=None, de
     )
 
 
+@functools.singledispatch
+def has_path(
+    graph,
+    source,
+    target,
+    as_undirected=False,
+):
+    """Checks if a path exists between a source and target node
+
+    :param graph: The input graph to use. Can either be a
+        :class:`~rustworkx.PyGraph` or :class:`~rustworkx.PyDiGraph`
+    :param int source: The node index to find paths from
+    :param int target: The index of the target node
+    :param bool as_undirected: If set to true the graph will be treated as
+        undirected for finding existence of a path. This only works with a
+        :class:`~rustworkx.PyDiGraph` input for ``graph``
+
+    :return: True if a path exists, False if not
+    :rtype: bool
+    """
+    raise TypeError("Invalid Input Type %s for graph" % type(graph))
+
+
+@has_path.register(PyDiGraph)
+def _digraph_has_path(graph, source, target, as_undirected=False):
+    return digraph_has_path(graph, source, target=target, as_undirected=as_undirected)
+
+
+@has_path.register(PyGraph)
+def _graph_has_path(graph, source, target):
+    return graph_has_path(graph, source, target=target)
+
+
 @functools.singledispatch
 def all_pairs_dijkstra_shortest_paths(graph, edge_cost_fn):
     """For each node in the graph, finds the shortest paths to all others.

src/lib.rs

@@ -400,6 +400,8 @@ fn rustworkx(py: Python<'_>, m: &PyModule) -> PyResult<()> {
     m.add_wrapped(wrap_pyfunction!(digraph_all_simple_paths))?;
     m.add_wrapped(wrap_pyfunction!(graph_dijkstra_shortest_paths))?;
     m.add_wrapped(wrap_pyfunction!(digraph_dijkstra_shortest_paths))?;
+    m.add_wrapped(wrap_pyfunction!(graph_has_path))?;
+    m.add_wrapped(wrap_pyfunction!(digraph_has_path))?;
     m.add_wrapped(wrap_pyfunction!(graph_dijkstra_shortest_path_lengths))?;
     m.add_wrapped(wrap_pyfunction!(digraph_dijkstra_shortest_path_lengths))?;
     m.add_wrapped(wrap_pyfunction!(graph_bellman_ford_shortest_paths))?;

src/shortest_path/mod.rs

@@ -109,6 +109,32 @@ pub fn graph_dijkstra_shortest_paths(
     })
 }
 
+/// Check if a graph has a path between source and target nodes
+///
+/// :param PyGraph graph:
+/// :param int source: The node index to find paths from
+/// :param int target: The index of the target node
+///
+/// :return: True if a path exists, False if not.
+/// :rtype: bool
+/// :raises ValueError: when an edge weight with NaN or negative value
+///     is provided.
+#[pyfunction]
+#[pyo3(
+    signature=(graph, source, target),
+    text_signature = "(graph, source, target)"
+)]
+pub fn graph_has_path(
+    py: Python,
+    graph: &graph::PyGraph,
+    source: usize,
+    target: usize,
+) -> PyResult<bool> {
+    let path_mapping = graph_dijkstra_shortest_paths(py, graph, source, Some(target), None, 1.0)?;
+
+    Ok(!path_mapping.paths.is_empty())
+}
+
 /// Find the shortest path from a node
 ///
 /// This function will generate the shortest path from a source node using
@@ -184,6 +210,36 @@ pub fn digraph_dijkstra_shortest_paths(
     })
 }
 
+/// Check if a digraph has a path between source and target nodes
+///
+/// :param PyDiGraph graph:
+/// :param int source: The node index to find paths from
+/// :param int target: The index of the target node
+/// :param bool as_undirected: If set to true the graph will be treated as
+///     undirected for finding a path
+///
+/// :return: True if a path exists, False if not.
+/// :rtype: bool
+/// :raises ValueError: when an edge weight with NaN or negative value
+///     is provided.
+#[pyfunction]
+#[pyo3(
+    signature=(graph, source, target, as_undirected=false),
+    text_signature = "(graph, source, target, /, as_undirected=false)"
+)]
+pub fn digraph_has_path(
+    py: Python,
+    graph: &digraph::PyDiGraph,
+    source: usize,
+    target: usize,
+    as_undirected: bool,
+) -> PyResult<bool> {
+    let path_mapping =
+        digraph_dijkstra_shortest_paths(py, graph, source, Some(target), None, 1.0, as_undirected)?;
+
+    Ok(!path_mapping.paths.is_empty())
+}
+
 /// Compute the lengths of the shortest paths for a PyGraph object using
 /// Dijkstra's algorithm
 ///

tests/rustworkx_tests/digraph/test_dijkstra.py

@@ -70,6 +70,21 @@ def test_dijkstra_path(self):
         }
         self.assertEqual(expected, paths)
 
+    def test_dijkstra_has_path(self):
+        g = rustworkx.PyDiGraph()
+        a = g.add_node("A")
+        b = g.add_node("B")
+        c = g.add_node("C")
+
+        edge_list = [
+            (a, b, 7),
+            (c, b, 9),
+            (c, b, 10),
+        ]
+        g.add_edges_from(edge_list)
+
+        self.assertFalse(rustworkx.digraph_has_path(g, a, c))
+
     def test_dijkstra_path_with_weight_fn(self):
         paths = rustworkx.digraph_dijkstra_shortest_paths(self.graph, self.a, weight_fn=lambda x: x)
         expected = {

tests/rustworkx_tests/graph/test_dijkstra.py

@@ -50,6 +50,21 @@ def test_dijkstra_path(self):
         expected = {4: [self.a, self.c, self.d, self.e]}
         self.assertEqual(expected, path)
 
+    def test_dijkstra_has_path(self):
+        g = rustworkx.PyGraph()
+        a = g.add_node("A")
+        b = g.add_node("B")
+        c = g.add_node("C")
+
+        edge_list = [
+            (a, b, 7),
+            (c, b, 9),
+            (c, b, 10),
+        ]
+        g.add_edges_from(edge_list)
+
+        self.assertTrue(rustworkx.graph_has_path(g, a, c))
+
     def test_dijkstra_with_no_goal_set(self):
         path = rustworkx.graph_dijkstra_shortest_path_lengths(self.graph, self.a, lambda x: 1)
         expected = {1: 1.0, 2: 1.0, 3: 1.0, 4: 2.0, 5: 2.0}