Adding Fuzz targets for lr planar (Qiskit#1434)

* Adding Fuzz targets for lr planar

Added a fuzz target to check the robustness of lr planar function.

* Fixing Lint

Author: Krishn1412

rustworkx-core/fuzz/Cargo.toml

@@ -42,6 +42,13 @@ test = false
 doc = false
 bench = false
 
+[[bin]]
+name = "test_fuzz_planar"
+path = "fuzz_targets/test_fuzz_planar.rs"
+test = false
+doc = false
+bench = false
+
 [[bin]]
 name = "test_fuzz_contraction"
 path = "fuzz_targets/test_fuzz_contraction.rs"

rustworkx-core/fuzz/fuzz_targets/test_fuzz_planar.rs

@@ -0,0 +1,39 @@
+#![no_main]
+
+use arbitrary::{Arbitrary, Unstructured};
+use libfuzzer_sys::fuzz_target;
+use rustworkx_core::petgraph::graph::UnGraph;
+use rustworkx_core::planar::is_planar;
+
+#[derive(Debug, Arbitrary)]
+struct FuzzGraph {
+    edges: Vec<(usize, usize)>,
+    node_count: usize,
+}
+
+fuzz_target!(|data: &[u8]| {
+    if let Ok(fuzz_input) = FuzzGraph::arbitrary(&mut Unstructured::new(data)) {
+        fuzz_check_is_planar(&fuzz_input);
+    }
+});
+
+fn fuzz_check_is_planar(input: &FuzzGraph) {
+    if input.node_count == 0 || input.edges.is_empty() || input.node_count > 1000 {
+        return;
+    }
+
+    let mut graph = UnGraph::<(), ()>::default();
+    let mut nodes = Vec::with_capacity(input.node_count);
+
+    for _ in 0..input.node_count {
+        nodes.push(graph.add_node(()));
+    }
+
+    for &(u, v) in &input.edges {
+        if u < input.node_count && v < input.node_count {
+            graph.add_edge(nodes[u], nodes[v], ());
+        }
+    }
+
+    let _ = is_planar(&graph);
+}