Fix includes and add some comments

algorithm/roditty_zwick.h

@@ -1,8 +1,6 @@
 #ifndef RODITTY_ZWICK_H_
 #define RODITTY_ZWICK_H_
 
-using namespace graph;
-
 namespace algo {
 
 template<typename T>
@@ -10,13 +8,14 @@ class RodittyZwick {
 public:
   ~RodittyZwick();
 
-  //
+  // This method is implemented and executed by all roditty and zwick
+  // algorithms, it constructs the data structures used in other operations
   virtual void init() =0;
 
-  //
+  // Answer if vertex v is reachable from vertex u
   virtual bool query(const T& u, const T& v) =0;
 
-  //
+  // Remove edge e(u,v) and maintain the transitive closure matrix
   virtual void remove(const T& u, const T& v) =0;
 };