Update decremental algorithms according to project structure changes

algorithm/italiano.h

@@ -1,37 +1,37 @@
 #ifndef ITALIANO_H_
 #define ITALIANO_H_
 
-#include "algorithm/roditty_zwick.h"
-#include "algorithm/tarjan.h"
+#include "algorithm/decremental_reachability.h"
 #include "graph/breadth_first_tree.h"
 
-#include <forward_list>
-#include <iostream>
-
 using namespace graph;
 
 namespace algo {
 
 template<typename T>
-class Italiano : public RodittyZwick<T> {
+class Italiano : public DecrementalReachability<T> {
 public:
-  Italiano(Digraph<T> G) : G(G) {}
+  Italiano() = default;
 
-  void init();
+  Italiano(Digraph<T> G) { this->G = G; }
 
-  bool query(const T& u, const T& v);
+  // Initialize the decremental maintenance data structure for DAGs
+  void init() override;
 
-  void remove(const T& u, const T& v);
+  // Execute reachability query q(u, v) from vertex u to vertex v
+  // in O(1) using the transitive closure matrix
+  bool query(const T& u, const T& v) override;
+
+  // Delete edge e(u, v) and explicitely maintain the transitive closure
+  void remove(const T& u, const T& v) override;
 private:
-  Digraph<T> G;
-
-  // Transitive closure matrix, used to answer reachability queries in O(1)
+  // Transitive closure matrix
   std::map<T, std::map<T, bool>> TC;
 
-  // Each vertex's reachability tree
+  // For each vertex, store a reachability tree created as a BFS tree
   std::map<T, BreadthFirstTree<T>> RT;
 
-  // Incoming / Outgoing edges
+  // For each vertex, store collections of its incoming and outgoing edges
   struct Edges {
     std::set<T> inc;
     std::set<T> out;
@@ -41,13 +41,13 @@ private:
 
 template<typename T>
 void Italiano<T>::init() {
-  for (const auto& u : G.vertices()) {
-    for (const auto& v : G.adjMatrix[u]) {
+  for (const auto& u : this->G.vertices()) {
+    for (const auto& v : this->G.adjMatrix[u]) {
       E[v].inc.insert(u);
       E[u].out.insert(v);
       TC[u][v] = false;
     }
-    RT[u] = BreadthFirstTree<T>(G, u);
+    RT[u] = BreadthFirstTree<T>(this->G, u);
     TC[u][u] = true;
     for (const auto& v : RT[u].vertices())
       TC[u][v] = true;
@@ -63,7 +63,7 @@ template<typename T>
 void Italiano<T>::remove(const T& u, const T& v) {
   std::map<T, std::stack<T>> H;
 
-  for (const auto& w : G.vertices()) {
+  for (const auto& w : this->G.vertices()) {
     if (RT[w].contains(u, v)) {
       if (E[v].inc.size() > 1)
         H[w].push(v);
@@ -77,9 +77,9 @@ void Italiano<T>::remove(const T& u, const T& v) {
 
   E[u].out.erase(v);
   E[v].inc.erase(u);
-  G.remove(u, v);
+  this->G.remove(u, v);
 
-  for (const auto& z : G.vertices()) {
+  for (const auto& z : this->G.vertices()) {
     RT[z].adjMatrix[u].erase(v);
     while (H[z].size() > 0) {
       auto& h = H[z].top();
@@ -87,11 +87,14 @@ void Italiano<T>::remove(const T& u, const T& v) {
       for (const auto& i : E[h].inc) {
         if (RT[z].contains(z, i)) {
           RT[z].adjMatrix[i].insert(h);
-          H[z].pop();
+          //
           found = true;
           break;
         }
       }
+      //
+      H[z].pop();
+      //
       if (!found) {
         TC[u][v] = false;
         for (const auto& o : E[h].out) {