From 065bffca3f3acd4804b581436b65c1bb7a0d5ef1 Mon Sep 17 00:00:00 2001
From: KARTHIKEYAN MUTHU <phenomenalkarthikeyan@gmail.com>
Date: Sun, 17 Mar 2024 15:35:33 -0400
Subject: [PATCH] Adding degree centrality function

---
 rustworkx-core/src/centrality.rs | 30 ++++++++++++++++++++++++++++++
 src/centrality.rs                | 20 ++++++++++++++++++++
 2 files changed, 50 insertions(+)

diff --git a/rustworkx-core/src/centrality.rs b/rustworkx-core/src/centrality.rs
index 35683bbc8..baf44a762 100644
--- a/rustworkx-core/src/centrality.rs
+++ b/rustworkx-core/src/centrality.rs
@@ -140,6 +140,36 @@ where
     betweenness
 }
 
+/// Computes the degree centrality of nodes in a graph.
+///
+/// Degree centrality is defined as the number of edges incident upon a node
+/// normalized by the maximum possible degree in a simple graph (n - 1, where n is the number of nodes).
+///
+/// Arguments:
+/// * `graph` - The graph object to compute degree centrality for.
+///
+/// Returns:
+/// A `Vec<f64>` containing the degree centrality of each node in the graph.
+pub fn degree_centrality<G>(graph: G) -> Result<Option<Vec<f64>>, E>
+    where
+        G: IntoNodeIdentifiers + NodeCount,
+    {
+        let num_nodes = graph.node_count() as f64;
+        let mut centrality_values = vec![0.0; graph.node_count()];
+    {
+            let degree = graph.edges(node).count() as f64;
+            let centrality = if num_nodes <= 1.0 {
+                0.0
+            } else {
+                degree / (num_nodes - 1.0)
+            };
+            centrality_values[graph.to_index(node)] = centrality;
+        }
+ 
+        Ok(Some(centrality_values))
+    }
+
+
 /// Compute the edge betweenness centrality of all edges in a graph.
 ///
 /// The algorithm used in this function is based on:
diff --git a/src/centrality.rs b/src/centrality.rs
index ca055cec3..c4b2a2ab7 100644
--- a/src/centrality.rs
+++ b/src/centrality.rs
@@ -97,6 +97,26 @@ pub fn graph_betweenness_centrality(
     }
 }
 
+/// A Python function wrapper for degree_centrality
+ 
+fn degree_centrality_py(
+    py: Python,
+    graph: &digraph::PyDiGraph,
+) -> PyResult<CentralityMapping> {
+    // Convert Python object to Rust type
+    let graph_rust = match graph.extract::<SomeRustGraphType>() {
+        Ok(g) => g,
+        Err(e) => return Err(e.into()), 
+    };
+    // Call the Rust function
+    match degree_centrality(graph_rust) {
+        Ok(Some(values)) => Ok(Some(values)),
+        Ok(None) => Ok(None),
+        Err(e) => Err(e.into()), 
+    }
+}
+ 
+
 /// Compute the betweenness centrality of all nodes in a PyDiGraph.
 ///
 /// Betweenness centrality of a node :math:`v` is the sum of the