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Graph.h
/* Retrieved from: http://en.literateprograms.org/Dijkstra's_algorithm_(C_Plus_Plus)?oldid=13422 */

#ifndef GRAPH_H
#define GRAPH_H

#include <vector>
#include <map>
#include <list>
#include <queue>
#include <set>

#undef min
#undef max
#include <limits>

#define Max(a,b) (((a) > (b)) ? (a) : (b))
#define Min(a,b) (((a) < (b)) ? (a) : (b))

template <typename VertexType = unsigned int, typename WeightType = double>
class Graph
{
private:
	typedef VertexType vertex_t;
	typedef WeightType weight_t;

public:
	struct Edge {
		vertex_t target;
		weight_t weight;
		unsigned int index;

		Edge(vertex_t arg_target, weight_t arg_weight, unsigned int edge_index = -1)
			: target(arg_target), weight(arg_weight), index(edge_index) { }

		bool operator == (const Edge & rhs) const
		{
			return (target == rhs.target && weight == rhs.weight && index == rhs.index);
		}
	};

	struct CompareEdge{
		bool operator()(const Edge &a, const Edge &b){
			if (a.target < b.target) return true;
			if (a.target > b.target) return false;
			return a.index < b.index;
		}
	};

	typedef std::set<Edge,CompareEdge> EdgesSet;

private:
	typedef std::map<vertex_t, std::list<Edge> > adjacency_map_t;
	typedef std::set<vertex_t> vertices_set;

	template <typename T1, typename T2>
	struct pair_first_less
	{
		bool operator()(std::pair<T1,T2> p1, std::pair<T1,T2> p2) const {
			if(p1.first == p2.first) {
				return p1.second < p2.second;
			}
			return p1.first < p2.first;
		}
	};

	void DijkstraComputePaths(vertex_t source)
	{
		if(source == lastStart)
			return;
		else
		{
			lastStart = source;
			previous.clear();
		}

		for (typename adjacency_map_t::iterator vertex_iter = adjacency_map.begin();
			vertex_iter != adjacency_map.end();
			vertex_iter++)
		{
			vertex_t v = vertex_iter->first;
			min_distance[v] = std::numeric_limits< WeightType >::infinity();
		}

		min_distance[source] = 0;
		std::set< std::pair<weight_t, vertex_t>,
			pair_first_less<weight_t, vertex_t> > vertex_queue;
		for (typename adjacency_map_t::iterator vertex_iter = adjacency_map.begin();
			vertex_iter != adjacency_map.end();
			vertex_iter++){
				vertex_t v = vertex_iter->first;
				vertex_queue.insert(std::pair<weight_t, vertex_t>(min_distance[v], v));
		}

		while (!vertex_queue.empty()) {
			vertex_t u = vertex_queue.begin()->second;
			vertex_queue.erase(vertex_queue.begin());

			// Visit each edge exiting u
			for (typename std::list<Edge>::iterator edge_iter = adjacency_map[u].begin();
				edge_iter != adjacency_map[u].end();
				edge_iter++)
			{
				vertex_t v = edge_iter->target;
				weight_t weight = edge_iter->weight;
				weight_t distance_through_u = min_distance[u] + weight;
				if (distance_through_u < min_distance[v]) {
					vertex_queue.erase(std::pair<weight_t, vertex_t>(min_distance[v], v));

					min_distance[v] = distance_through_u;
					previous[v] = u;
					vertex_queue.insert(std::pair<weight_t, vertex_t>(min_distance[v], v));
				}

			}
		}
	}

	std::list<vertex_t> DijkstraGetShortestPathTo(vertex_t target)
	{
		std::list<vertex_t> path;
		typename std::map<vertex_t, vertex_t>::iterator prev;
		vertex_t vertex = target;

		path.push_front(vertex);

		while((prev = previous.find(vertex)) != previous.end())
		{
			vertex = prev->second;
			path.push_front(vertex);
		}

		return path;
	}

public:
	std::list<vertex_t> DijkstraShortestPath(vertex_t start, vertex_t end)
	{
		this->DijkstraComputePaths(start);
		return this->DijkstraGetShortestPathTo(end);
	}

	int NodeDistance(vertex_t n1, vertex_t n2)
	{
		if(!this->isConnected(n1, n2)) return -1;
		return DijkstraShortestPath(n1, n2).size();
	}

private:
	// Graph Variables:
	vertices_set vertices;
	adjacency_map_t adjacency_map;

	std::map<vertex_t, weight_t> min_distance;
	std::map<vertex_t, vertex_t> previous;

	vertex_t lastStart;

public:

	Graph()
	{
		lastStart = std::numeric_limits<vertex_t>::max();
	}

	Graph(const Graph& from)
	{
		this->adjacency_map = from.adjacency_map;
		this->vertices = from.vertices;
		this->min_distance = from.min_distance;
		this->previous = from.previous;
		this->lastStart = from.lastStart;
	}

	void AddEdge(vertex_t p1, vertex_t p2, weight_t weight, int index = -1)
	{
		adjacency_map[AddVertex(p1)].push_back(Edge(AddVertex(p2), weight, index));
		adjacency_map[AddVertex(p2)].push_back(Edge(AddVertex(p1), weight, index));
	}

	vertex_t AddVertex(vertex_t p)
	{
		vertices.insert(p);

		return p;
	}

	void removeDirectedEdge(vertex_t p1, vertex_t p2)
	{
		std::list<Edge> * adj = &adjacency_map[p1];

		for(typename std::list<Edge>::iterator i = adj->begin(); i != adj->end(); i++)
		{
			Edge * e = &(*i);

			if(e->target == p2)
			{
				adj->remove(*e);
				return;
			}
		}
	}

	void removeEdge(vertex_t p1, vertex_t p2)
	{
		removeDirectedEdge(p1, p2);
		removeDirectedEdge(p2, p1);
	}

	void SetDirectedEdgeWeight(vertex_t p1, vertex_t p2, weight_t newWeight)
	{
		std::list<Edge> * adj = &adjacency_map[p1];

		for(typename std::list<Edge>::iterator i = adj->begin(); i != adj->end(); i++)
		{
			Edge * e = &(*i);

			if(e->target == p2)
			{
				e->weight = newWeight;
				return;
			}
		}
	}

	void SetEdgeWeight(vertex_t p1, vertex_t p2, weight_t newWeight)
	{
		SetDirectedEdgeWeight(p1, p2, newWeight);
		SetDirectedEdgeWeight(p2, p1, newWeight);
	}

	vertex_t GetRandomNeighbour(vertex_t p)
	{
		return adjacency_map[p].front().target;
	}

	std::vector<vertex_t> GetNeighbours(vertex_t p)
	{
		std::vector<vertex_t> neighbours;

		std::list<Edge> * adj = &adjacency_map[p];

		for(typename std::list<Edge>::iterator i = adj->begin(); i != adj->end(); i++)
		{
			Edge * e = &(*i);

			neighbours.push_back(e->target);
		}

		return neighbours;
	}

	vertex_t GetOtherNeighbour(vertex_t p, vertex_t q)
	{
		vertex_t n = p;

		std::list<Edge> * adj = &adjacency_map[p];
		for(typename std::list<Edge>::iterator i = adj->begin(); i != adj->end(); i++)
		{
			Edge * e = &(*i);

			if(e->target != q)
			{
				n = e->target;
				break;
			}
		}

		return n;
	}

	bool isCircular(vertex_t p)
	{
		std::set<vertex_t> visited;

		visited.insert(p);

		bool hasMore = true;

		vertex_t curr = p;
		vertex_t prev = p;

		while(hasMore)
		{
			vertex_t next = GetOtherNeighbour(curr, prev);

			if(next == curr)
				return false;

			if(visited.find(next) != visited.end())
				return true;

			prev = curr;
			curr = next;
		}

		return false;
	}

	bool isConnected(vertex_t v1, vertex_t v2)
	{
		this->DijkstraComputePaths(v1);

		if(min_distance[v2] != std::numeric_limits< WeightType >::infinity())
			return true;

		return false;
	}

	vertices_set GetNodes()
	{
		return vertices;
	}

	// the 'index' of the edge will be replaced with index of a vertex
	std::vector<Edge> GetEdges()
	{
		std::vector<Edge> result;

		for(typename adjacency_map_t::iterator it = adjacency_map.begin(); it != adjacency_map.end(); it++)
		{
			vertex_t v1 = it->first;
			std::list<Edge> adj = it->second;

			for(typename std::list<Edge>::iterator i = adj.begin(); i != adj.end(); i++)
			{
				Edge e = *i;

				result.push_back(Edge(Min(e.target, v1), e.weight, Max(e.target, v1)));
			}
		}

		return result;
	}

	EdgesSet GetEdgesSet()
	{
		std::vector<Edge> allEdges = GetEdges();

		EdgesSet result;

        for(typename std::vector<Edge>::iterator it = allEdges.begin(); it != allEdges.end(); it++)
			result.insert(*it);

		return result;
	}

	std::vector<vertex_t> GetLeaves() const
	{
		std::vector<vertex_t> leaves;

		for(typename adjacency_map_t::const_iterator it = adjacency_map.begin(); it != adjacency_map.end(); it++)
		{
			if(it->second.size() < 2)
				leaves.push_back(it->first);
		}

		return leaves;
	}

	void explore(vertex_t seed, std::set<vertex_t> & explored)
	{
		std::queue<vertex_t> q;

		q.push(seed);
		explored.insert(seed);

		while(!q.empty())
		{
			vertex_t i = q.front();
			q.pop();

			std::list<Edge> * adj = &adjacency_map[i];
			for(typename std::list<Edge>::const_iterator it = adj->begin(); it != adj->end(); it++)
			{
				vertex_t j = it->target;

				// Check: not visited
				if(explored.find(j) == explored.end()) 
				{
					explored.insert(j);
					q.push(j);
				}
			}
		}
	}

	vertex_t getNodeLargestConnected()
	{
		std::vector< std::set<vertex_t> > connectedComponents;
		std::set<vertex_t> unvisited;

		if(vertices.size() == 0)
			return -1;

		// fill unvisited set
		for(typename vertices_set::const_iterator it = vertices.begin(); it != vertices.end(); it++)
			unvisited.insert(*it);

		while(unvisited.size() > 1)
		{
			// Take first unvisited node
			vertex_t firstNode = *(unvisited.begin());

			// Explore its tree
			std::set<vertex_t> currVisit;
			currVisit.insert(firstNode);
			explore(firstNode, currVisit);

			// Add as a connected component
			connectedComponents.push_back(currVisit);

			// Remove from unvisited set
			for(typename std::set<vertex_t>::iterator it = currVisit.begin(); it != currVisit.end(); it++)
				unvisited.erase(*it);
		}

		// Find set with maximum number of nodes
		int maxConnectSize = -1, max_i = 0;
		for(int i = 0; i < (int)connectedComponents.size(); i++)
		{
			int currSize = connectedComponents[i].size();

			if(currSize > maxConnectSize){
				maxConnectSize = currSize;
				max_i = i;
			}
		}

		// Return first node of that maximum set
		return *(connectedComponents[max_i].begin());
	}

	std::set<vertex_t> GetLargestConnectedComponent()
	{
		std::vector<std::set<vertex_t> > connectedComponents;
		std::set<vertex_t> unvisited;

		// fill unvisited set
		for(typename vertices_set::const_iterator it = vertices.begin(); it != vertices.end(); it++)
			unvisited.insert(*it);

		while(unvisited.size() > 1)
		{
			// Take first unvisited node
			vertex_t firstNode = *(unvisited.begin());

			// Explore its tree
			std::set<vertex_t> currVisit;
			currVisit.insert(firstNode);
			explore(firstNode, currVisit);

			// Add as a connected component
			connectedComponents.push_back(currVisit);

			// Remove from unvisited set
			for(typename std::set<vertex_t>::iterator it = currVisit.begin(); it != currVisit.end(); it++)
				unvisited.erase(*it);
		}

		// Find set with maximum number of nodes
		int maxConnectSize = -1, max_i = 0;
		for(int i = 0; i < (int)connectedComponents.size(); i++)
		{
			int currSize = connectedComponents[i].size();

			if(currSize > maxConnectSize){
				maxConnectSize = currSize;
				max_i = i;
			}
		}

		// Return first node of that maximum set
		return connectedComponents[max_i];
	}

	void subGraph(Graph & g, const std::set<vertex_t> & explored)
	{
        for(typename std::set<vertex_t>::const_iterator vi = explored.begin(); vi != explored.end(); vi++)
		{
			std::list<Edge> adj = g.adjacency_map[*vi];

            for(typename std::list<Edge>::iterator e = adj.begin(); e != adj.end(); e++)
				this->AddEdge(*vi, e->target, e->weight);
		}
	}

	std::vector< Graph <vertex_t,weight_t> > toConnectedParts()
	{
		std::vector< Graph <vertex_t,weight_t> > result;

		// Make a 'bitmap' of visited nodes
		std::map<vertex_t, bool> isVisited;
        for(typename std::set<vertex_t>::iterator it = vertices.begin(); it != vertices.end(); it++)
			isVisited[*it] = false;
		
        for(typename std::map<vertex_t,bool>::iterator i = isVisited.begin(); i != isVisited.end(); i++)
		{
			// Check if visited
			if(i->second)
				continue;

			vertex_t seed = i->first;

			std::set<vertex_t> explored;
			explore(seed, explored);

			// Add this new connected sub graph from exploration
			result.push_back(Graph<vertex_t, weight_t>());
			result.back().subGraph(*this, explored);

			// mark as visited the explored
            for(typename std::set<vertex_t>::iterator vi = explored.begin(); vi != explored.end(); vi++)
				isVisited[*vi] = true;
		}
	
		return result;
	}

	std::list<vertex_t> GetLargestConnectedPath()
	{
		std::list<vertex_t> longestPath;

		std::set<vertex_t> seedSet = GetLargestConnectedComponent(); 
		std::vector<vertex_t> leaves = GetLeaves();

		if(!leaves.size())
		{
			leaves.push_back(*this->vertices.begin());
		}

		vertex_t seed = leaves.front();

		DijkstraComputePaths(seed);

        for(typename std::set<vertex_t>::iterator it = seedSet.begin(); it != seedSet.end(); it++)
		{
			std::list<vertex_t> curPath = DijkstraGetShortestPathTo(*it);

			if(curPath.size() > longestPath.size())
				longestPath = curPath;
		}

		return longestPath;
	}

	bool CheckAdjacent(vertex_t v1, vertex_t v2)
	{
		if(v1 == v2) return true;

        for(typename std::list<Edge>::iterator e = adjacency_map[v1].begin(); e != adjacency_map[v1].end(); e++)
			if(e->target == v2) return true;

		return false;
	}
};

#endif // GRAPH_H
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