qyshortestpath.cpp

在GRAPH中找出K條最短路徑,並且輸出到SP.txt檔中

// ____________________________________________________________________________
//
//  General Information:
//
//  File Name:      QYShortetsPath.cpp
//  Author:         Yan Qi
//  Project:        KShortestPath
//
//  Description:    Implementation of class(es) CQYShortestPath
//
//  - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
//  Revision History:
//
//  11/23/2006   Yan   Initial Version
//
//  - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
//  Copyright Notice:
//
//  Copyright (c) 2006 Your Company Inc.
//
//  Warning: This computer program is protected by copyright law and
//  international treaties.  Unauthorized reproduction or distribution
//  of this program, or any portion of it, may result in severe civil and
//  criminal penalties, and will be prosecuted to the maximum extent
//  possible under the law.
//
// ____________________________________________________________________________
//#pragma warning(disable: 4786)
#include <iostream>
#include <boost/graph/dijkstra_shortest_paths.hpp>
#include "QYShortestPath.h"

namespace asu_emit_qyan
{
    using namespace std;

	/* Default Constructor*/
	/************************************************************************/
	CQYShortestPath::CQYShortestPath( const CQYDirectedGraph& rGraph ) : m_rGraph(rGraph)
	{
		m_nSourceNodeId = -1; // the source node id is 0 by default.
		_Init();
	}

	CQYShortestPath::~CQYShortestPath()	{}


	/************************************************************************/
	/* Initiate members */
	/************************************************************************/
	void CQYShortestPath::_Init()
	{
		int vertices_count = m_rGraph.GetNumberOfVertices();

		// First: edges with weights
		for (int i=0; i!=vertices_count; ++i)
		{
			for (int j=0; j!=vertices_count; ++j)
			{
				if (m_rGraph.GetWeight(i,j) != CQYDirectedGraph::DISCONNECT)
				{
					m_vEdges.push_back(Edge_Type(i,j));
					m_vWeights.push_back(m_rGraph.GetWeight(i,j));
				}
			}
		}
	}

	/************************************************************************/
	/* Analysis of m_vResult4Vertices and m_vResult4Distance to generate the shortest path.*/
	/************************************************************************/
	CQYDirectedPath* CQYShortestPath::_GetShortestPath( int nTargetNodeId )
	{
		vector<int> vertex_list;

		// Check the input
		if (nTargetNodeId >= m_rGraph.GetNumberOfVertices() || nTargetNodeId < 0)
		{
			std::cerr << "Please enter a right terminal id!" << std::endl;
			return new CQYDirectedPath(-1, CQYDirectedGraph::DISCONNECT, vertex_list);
		}

		if (m_distanceMap[nTargetNodeId] == CQYDirectedGraph::DISCONNECT)
		{
			std::cerr << "The path doesn't exist!" << std::endl;
			return new CQYDirectedPath(-2, CQYDirectedGraph::DISCONNECT, vertex_list);
		}

		// Determine the shortest path from the source to the terminal.
		int cur_vertex = nTargetNodeId;
		list<int> tmp_list;
		tmp_list.push_front(nTargetNodeId);
		do
		{
			if (m_nextNodeMap[cur_vertex] == m_nSourceNodeId)
			{
				if(cur_vertex != m_nSourceNodeId) tmp_list.push_front(m_nSourceNodeId);
				break;
			}else
			{
				cur_vertex = m_nextNodeMap[cur_vertex];
				tmp_list.push_front(cur_vertex);
			}
		} while(1);
		//
		copy(tmp_list.begin(), tmp_list.end(), back_inserter(vertex_list));

		//
		return new CQYDirectedPath(0, m_distanceMap[nTargetNodeId], vertex_list);
	}

	/************************************************************************/
	/* Calculate the shortest path from a source to a target. */
	/************************************************************************/
	CQYDirectedPath* CQYShortestPath::GetShortestPath( int nSourceNodeId, int nTargetNodeId )
	{
		if (m_nSourceNodeId != nSourceNodeId)
		{
			m_nSourceNodeId = nSourceNodeId;
			_DijkstraShortestPathsAlg();
		}

		return _GetShortestPath(nTargetNodeId);
	}

	/************************************************************************/
	/* Based on the input - the source of the path, create a steiner tree. (???)*/
	/************************************************************************/
	void CQYShortestPath::ConstructPathTree( int nSourceNodeId )
	{
		m_nSourceNodeId = nSourceNodeId;
		_DijkstraShortestPathsAlg();
	}

	/************************************************************************/

	/************************************************************************/
	void CQYShortestPath::_DijkstraShortestPathsAlg()
	{
		int edges_count = m_rGraph.GetNumberOfEdges();
		int vertices_count = m_rGraph.GetNumberOfVertices();

		//////////////////////////////////////////////////////////////////////////
		// Initiate the boost graph
		vector<Vertex_Descriptor> vResult4Vertices;
		vector<double> vResult4Distance;
		Boost_Graph_Type g(vertices_count);
		property_map<Boost_Graph_Type, edge_weight_t>::type weightmap = get(edge_weight, g);
		//
		for (std::size_t j = 0; j < edges_count; ++j)
		{
			Edge_Descriptor e; bool inserted;
			tie(e, inserted) = add_edge(m_vEdges[j].first, m_vEdges[j].second, g);
			weightmap[e] = m_vWeights[j];
		}

		// about the vertices in the boost graph
		vResult4Vertices.resize(num_vertices(g));
		vResult4Distance.resize(num_vertices(g));
		Vertex_Descriptor s = vertex(m_nSourceNodeId, g);

		// run the algorithm
		// VC++ has trouble with the named parameters mechanism
		property_map<Boost_Graph_Type, vertex_index_t>::type indexmap = get(vertex_index, g);
		dijkstra_shortest_paths(g, s, &vResult4Vertices[0], &vResult4Distance[0], weightmap, indexmap,
			std::less<double>(), closed_plus<double>(),
			CQYDirectedGraph::DISCONNECT, 0, default_dijkstra_visitor());

		//////////////////////////////////////////////////////////////////////////
		// Set the results
		for (int i=0; i<vResult4Vertices.size(); ++i)
		{
			m_distanceMap[i] = vResult4Distance[i];
			m_nextNodeMap[i] = vResult4Vertices[i];
		}

	}
}