Added indexing of edges to graph class

bnb/graph.cpp

@@ -7,6 +7,31 @@ unsigned int graph::num_nodes() const {
     return nodes_;
 }
 
+unsigned int graph::num_edges() const {
+    return indexed_edges_.size();
+}
+
 const std::vector<unsigned int>& graph::get_adjacency(node_id v) const {
     return adjacency_list_[v-1];
 }
+
+void graph::index_edges() {
+	unsigned int nodes = num_nodes();
+	unsigned int eid = 0;
+	
+	for (node_id u = 1; u <= nodes; u++) {
+		const std::vector<node_id> & neighbors = get_adjacency(u);
+        
+		for (node_id v : neighbors) {			
+            if (u < v) {
+                auto node_pair = std::make_pair(u, v);
+                indexed_edges_[node_pair] = eid;
+                eid++;
+            }
+		}
+	}
+}
+
+unsigned int graph::get_edge_id(node_id u, node_id v) const {
+    return indexed_edges_.at(std::make_pair(u, v));
+}

include/gp-bnb/graph.hpp

@@ -2,6 +2,7 @@
 #define GRAPH_HPP
 
 #include <vector>
+#include <map>
 
 using node_id = unsigned int; 
 
@@ -18,6 +19,16 @@ public:
      *  @return Number of nodes
      */
     unsigned int num_nodes() const;
+
+    /** @brief  Returns the number of edges in the graph
+     *  @return Number of edges after have been indexed
+     */
+    unsigned int num_edges() const;
+
+    /**
+	 * @brief Indexes edges of the graph
+	 */
+    void index_edges();
     
     /** @brief  Provides access to the adjacency of a node  
      *  @param  Node Id
@@ -25,9 +36,16 @@ public:
      */
     const std::vector<unsigned int>& get_adjacency(node_id v) const;
 
+    /** @brief  Returns the id of an edge after calling index_edges()
+     *  @param  Two Node ids (u, v)
+     *  @return Edge id
+     */
+    unsigned int get_edge_id(node_id u, node_id v) const;
+
 private:
     unsigned int nodes_;
 	std::vector<std::vector<unsigned int>> adjacency_list_;
+    std::map<std::pair<node_id, node_id>, unsigned int> indexed_edges_;
 };
 
 #endif