/*
 *  Simple (Directed) Graph Data Structure
 *  <mjd@cs.auckland.ac.nz> -- Sept 2002
 */
#ifndef GRAPH_H
#define GRAPH_H

#include <iostream>
#include <vector>
#include <cmath>
#include <cassert>
#include <algorithm>

using namespace std;

typedef vector<int> NLIST;    		// node (neighbor) list
typedef vector< NLIST > ADJLIST;  	// graph data structure

class Graph
{
private:

   ADJLIST adj;  // adjacency lists.

public:  
   // creators + destroyers
   //
   Graph(int n) : adj(n) { }
   ~Graph() {}

   // stream I/0
   //
   friend ostream& operator<<(ostream&, const Graph&);
   friend istream& operator>>(istream&, Graph&);

   // mutators
   //
   bool addArc(int u, int v)  // false if already exists
   {
     if ( isArc(u,v) ) return false;
  
     adj[u].push_back(v);
     return true;
   }

   bool addEdge(int u, int v) // bi-directional arcs
   {
     return addArc(u,v) && addArc(v,u);
   }

   bool rmArc(int u, int v)  // false if doesn't exist
   {
     int n = order();
     assert(u >= 0 && u < n);
     assert(v >= 0 && v < n);
     assert(u != v);

     const NLIST::iterator it = find( adj[u].begin(), adj[u].end(), v );
     if ( it==adj[u].end() ) return false;
     adj[u].erase(it);
     return true;
   }

   bool rmEdge(int u, int v)
   {
     return rmArc(u,v) && rmArc(v,u);
   }

   // accessors
   //
   int order() const { return adj.size(); }

   bool isArc(int u, int v) const
   {
     int n = order();
     assert(u >= 0 && u < n);
     assert(v >= 0 && v < n);
     assert(u != v);
  
     NLIST::const_iterator it = find( adj[u].begin(), adj[u].end(), v );
     if ( it==adj[u].end() ) return false;
     else return true;
   }

   bool isEdge(int u, int v) const
   {
     return isArc(u,v) && isArc(v,u);
   }

   // out-degree
   int degree(int u) const { return adj[u].size(); }

   const NLIST neighbors(int u) const { return (const NLIST&) adj[u]; }

};

#endif