/********************************************************************
  Author:        Dana Vrajitoru, IUSB, CS
  Class:         C243, Spring 2004
  File name:     graph.cc
  Last updated:  April 20, 2004.
  Description:   Implementation of a class that implements a graph.
*********************************************************************/

#include "graph.h"
#include <fstream>
#include <iostream>
#include <iomanip>

// Default constructor - makes an empty undirected graph.
Graph::Graph()
{
  nr_vertices = 0;
  nr_edges = 0;
  directed = false;
}

// Destructor - empty the lists and the vector.
Graph::~Graph()
{
  Make_empty();
}

// Starts the graph over.
void Graph::Make_empty()
{
  if (nr_vertices) {
    for (int i=0; i<nr_vertices; i++) 
      edge_list[i].clear();
    edge_list.erase(edge_list.begin(), edge_list.end());
    nr_vertices = 0;
    nr_edges = 0;
  }
}

// Initializes the edge_list vector based on the number of vertices.
void Graph::Init(int vertexnr)
{
  List_int l;
  for (int i=0; i<vertexnr; i++)
    edge_list.push_back(l);
  nr_vertices = vertexnr;
}

// Set the direction flag to directed or undirected.
void Graph::Set_directed()
{
  directed = true;
}

void Graph::Set_undirected()
{
  directed = false;
}

// Adds an edge between vertices identified by their index
void Graph::Add_edge(const int index1, const int index2)
{
  if (index1 < nr_vertices && index2 < nr_vertices) {
    edge_list[index1].push_back(index2);
    if (!directed)
      edge_list[index2].push_back(index1);
    nr_edges++;
  }
  else
    cout << "Attempting to add an edge with nonexisting vertex." << endl;
}

// Reads the graph from a file
void Graph::Read(const char *filename)
{
  directed=true;
  ifstream fin(filename);
  int nrv, v1, v2;    
  fin >> nrv;
  Init(nrv);
  while (!fin.eof()) {
    fin >> v1 >> v2;
    if (fin.good())
      Add_edge(v1, v2);
  }
  fin.close();
}

// Simple print of the graph.
void Graph::Print()
{
  int i;
  if (directed)
    cout << "The graph is directed" << endl;
  else
    cout << "The graph is undirected" << endl;
  cout << "The graph contains " << nr_vertices
       << " vertices and " << nr_edges << " edges" << endl;
  if (nr_vertices) {
    cout << "The adjacency list for each vertex is:" << endl;
    for (i=0; i<nr_vertices; i++) {
      cout << "vertex " << i << ": ";
      List_int_iter iter;
      iter = edge_list[i].begin();
      while (iter != edge_list[i].end()) {
	cout << *iter << ' ';
	iter++;
      }
      cout << endl;
    }
  }
}

// Function to be implemented by the students.

// Count the number of edges ending with the vertex v. In other
// words, the number of times v is featured in any of the adjagency
// lists (neighbors).
int Graph::Count_incoming(int v)
{
  // Statement included for compilation.
  return 0;
}