Add BreadthFirstTree's to decremental maintenance algorithm and delete In/Out tree classes

algorithm/decremental_scc.h

@@ -7,6 +7,7 @@
 #include "tree/breadth_first_tree.h"
 
 using namespace graph;
+using namespace tree;
 
 namespace algo {
 
@@ -28,10 +29,9 @@ private:
   // Array used to answer strong connectivity queries in O(1) time
   std::map<T, T> A;
 
-  // Connect SCC/SCC representative with 2 SPTs
-  // pair.first: Shortest-paths out-tree
-  // pair.second: Shortest-paths in-tree
-  std::map<T, std::pair<Digraph<T>, Digraph<T>>> SPT;
+  // Maintain in-out bfs trees
+  std::map<T, BreadthFirstTree<T>> inTree;
+  std::map<T, BreadthFirstTree<T>> outTree;
 
   // Connect each representative with its SCC
   std::map<T, SCC<T>> connection;
@@ -49,15 +49,14 @@ void DecrementalSCC<T>::findSCC() {
   for (auto& C : SCCs) {
     const auto& w = C.representative();
 
-    // Create shortest-paths out-tree/in-tree
-    auto outTree = Digraph<T>(BreadthFirstSearch<T>(C).execute(w));
-    SPT[w] = std::make_pair(outTree, outTree.reverse());
-
-    // Update A with current SCCs vertices
     for (const auto& v : C.vertices)
       A[v] = w;
+    
+    outTree[w] =
+      BreadthFirstTree<T>(BreadthFirstSearch<T>(C).execute(w));
+    inTree[w] =
+      BreadthFirstTree<T>(BreadthFirstSearch<T>(C.reverse()).execute(w));
 
-    // Link SCC with its representative w
     connection[w] = C;
   }
 }
@@ -69,30 +68,27 @@ bool DecrementalSCC<T>::query(const T& u, const T& v) {
 
 template<typename T>
 void DecrementalSCC<T>::remove(const T& u, const T& v) {
+  G.adjMatrix[u].erase(v);
+
   // If u and v are not in the same SCC, do nothing
   if (A[u] != A[v]) return;
 
   const auto& w = A[u];
+  connection[w].remove(u, v);
 
-  // If edge e(u, v) is not contained in In(w) and Out(w), do nothing
-  if (!SPT[w].first.vertices.contains(w) &&
-      !SPT[w].second.vertices.contains(w)){
-    connection[w].adjMatrix[u].erase(v);
-    G.adjMatrix[u].erase(v);
-    return;
+  // Update In(w) and Out(w) if they contain the edge
+  if (inTree[w].contains(u, v) || outTree[w].contains(u, v)) {
+    auto C = connection[w];
+    inTree[w] =
+      BreadthFirstTree<T>(BreadthFirstSearch<T>(C.reverse()).execute(w));
+    outTree[w] =
+      BreadthFirstTree<T>(BreadthFirstSearch<T>(C).execute(w));
   }
-  // Update In(w) and Out(w)
-  connection[w].adjMatrix[u].erase(v);
-  G.adjMatrix[u].erase(v);
-  auto inTree = Digraph<T>(BreadthFirstSearch<T>(connection[w]).execute(w));
-  SPT[w] = std::make_pair(inTree, inTree.reverse());
 
   // If a SCC is broken, compute all SCCs again
-  if (!SPT[w].second.vertices.contains(u) ||
-      !SPT[w].first.vertices.contains(v)) {
+  if (!inTree[w].contains(u) || !outTree[w].contains(v)) {
     findSCC();
   }
-
 }
 
 }; // namespace algo