C++ graph::isEdge方法代码示例

void findSpanningForest(graph &g, graph &sf)
	// Create a graph sf that contains a spanning forest on the graph g.
{
	if (isConnected(g) && !isCyclic(g))
	{
		sf = g;
	}
	else
	{
		// add nodes to sf
		for (int i = 0; i < g.numNodes(); i++)
		{
			sf.addNode(g.getNode(i));
		}

		// build sf
		for (int i = 0; i < g.numNodes(); i++)
		{
			for (int j = 0; j < g.numNodes(); j++)
			{
				if (g.isEdge(i, j) && !sf.isEdge(i, j))
				{
					sf.addEdge(i, j, g.getEdgeWeight(i, j));
					sf.addEdge(j, i, g.getEdgeWeight(j, i));

					if(isCyclic(sf))
					{
						sf.removeEdge(j, i);
						sf.removeEdge(i, j);
					} // if
				} // if
			} // for
		} // for
	} // else
} // findSpanningForest

int getNumComponents(graph &g)
{
   g.clearMark();
   g.clearVisit();
   int numComponents = 0;
   queue<int> currentMoves;
   for (int n=0;n<g.numNodes();n++)
   {
      if (!g.isVisited(n))
      {  
         numComponents++;
         int nodeNumber=n;
         g.visit(nodeNumber);
         currentMoves.push(nodeNumber);
         while(currentMoves.size() > 0)
         {
            int currentNode = currentMoves.front();
            currentMoves.pop();
            //Populate a list of nodes that can be visited
            for (int i=0;i<g.numNodes();i++)
            {
               if (g.isEdge(currentNode,i) && !g.isVisited(i))
               {
                  g.mark(currentNode,i);
                  g.visit(i);
                  currentMoves.push(i);
               }
            }
         }
      }
   }
   return numComponents;
}

bool isConnected(graph &g)
// Returns true if the graph g is connected.  Otherwise returns false.
{
	queue<int> que;
	int id=0,count=1;

	que.push(id);
	g.visit(id);

	while(count<g.numNodes() && !que.empty())
	{
		id=que.front();
		for(int i=0;i<g.numNodes();i++)
		{
			if (g.isEdge(id,i) && !g.isVisited(i))
			{
				g.visit(i);
				que.push(i);
				count++;
			}
		}
		que.pop();                                                                                                                                                                                                                                                                                                                                                                                                                                                          
	}

	for (int z=0;z<g.numNodes();z++)
		g.unVisit(z);

	if(count==g.numNodes())
		return true;
	else return false;
}

edgepair getMinEdge(graph &g)
// iterate through whole graph and finds the edge from 
// marked node to unmarked node with minimum weight
// returns a struct with marked, unmarked, and weight
{
    int minCost = HIGH;
    int marked = NONE;
    int unmarked = NONE;
    
    // find the minimum edge
    for (int i = 0; i < g.numNodes() ; i++)
    {
        if (g.isMarked(i))
        {
            for (int j = 0; j < g.numNodes(); j++)
            {
                if (!g.isMarked(j) && g.isEdge(i, j) && g.getEdgeWeight(i, j) < minCost) 
                {
                    minCost = g.getEdgeWeight(i,j);
                    marked = i;
                    unmarked = j;
                }
            }
        }
    }

    edgepair pair = {marked, unmarked, minCost};
    return pair;
}

void findMSF(graph &g, graph &sf, int start)
	// finds a minimum spanning tree in graph 'g'
{
	priority_queue<edge, vector<edge>, CompareEdge> pq;
	vector<int> lst = getNeighbors(start, g);

	// build our priority queue
	for (int i = 0; i < lst.size(); i++)
	{
		pq.push(g.getEdge(start, lst[i]));
		g.mark(start, lst[i]);
	}

	// visit the start node
	g.visit(start);

	int src, dst, w;
	edge top;

	while (!pq.empty())
	{
		top = pq.top();
		pq.pop();
		src = top.getSource();
		dst = top.getDest();
		w = top.getWeight();

		// add edges
		if (!sf.isEdge(src, dst))
		{
			sf.addEdge(src, dst, w);
			sf.addEdge(dst, src, w);

			// delete edges if we make a cycle
			if (isCyclic(sf))
			{
				sf.removeEdge(src, dst);
				sf.removeEdge(dst, src);
			}
			else
			{
				g.visit(src);
				lst = getNeighbors(dst, g);

				for (int i = 0; i < lst.size(); i++)
				{
					if (!g.isMarked(dst, lst[i]))
					{
						pq.push(g.getEdge(dst, lst[i]));
						g.mark(dst, lst[i]);
					}
				} // for
			} // else
		} // if
	} // while
} // findMSF

vector<int> getNeighbors(graph &g, int current)
// loops through nodes and check if there is an edge between
// current and node, returns a vector of neighboring nodes
{
    vector<int> neighbors;
    for (int i = 0; i < g.numNodes(); i++)
    {
        if (g.isEdge(current, i))
            neighbors.push_back(i);
    }
    return neighbors;
}

bool isCyclic(graph &g)
// Returns true if the graph g contains a cycle.  Otherwise, returns false.
{
	queue<int> que;
	int id=0,count=1;
	bool first=true;
	vector<int> parentCount(g.numNodes(),-1);

	que.push(id);
	g.visit(id);

	while(count<g.numNodes() || !que.empty())
	{
		if (que.empty())
		{
			id=count;
			que.push(id);
			g.visit(id);
			count++;
		}
		else
			id=que.front();

		for(int i=0;i<g.numNodes();i++)
		{
			if (g.isEdge(id,i) && i!=que.front())
			{
				if(!g.isVisited(i))
				{
					g.visit(i);
					que.push(i);
					count++;
					parentCount[i]=id;
				}
				else if(parentCount[id]==i)
					continue;
				else
				{
					for (int z=0;z<g.numNodes();z++)
						g.unVisit(z);
					return true;
				}
			}
		}
		que.pop();    
	}

	for (int z=0;z<g.numNodes();z++)
		g.unVisit(z);

	return false;
}

vector<int> getNeighbors(int id, graph &g)
	// get all neighbors of the node (id) in the graph (g)
{
	vector<int> lst;

	for (int i = 0; i < g.numNodes(); i++)
	{
		if (g.isEdge(id, i))
		{
			lst.push_back(i);
		}
	} // for
	return lst;
} // getNeighbors

vector<int> getNeighbors(int id, graph &g)
// get all neighbors of the node with given id in graph g
{
    vector<int> lst;
    for (int i = 0; i < g.numNodes(); i++)
    {
        if (g.isEdge(id, i))
        {
            lst.push_back(i);
        }
    }

    return lst;
}

void findSpanningForest(graph &g, graph &sf)
// Create a graph sf that contains a spanning forest on the graph g.
{
	queue<int> que;
	int id=0,count=1;
	bool first=true;
	vector<int> parentCount(g.numNodes(),-1);

	que.push(id);
	g.visit(id);

	while(count<g.numNodes() || !que.empty())
	{
		if (que.empty())
		{
			id=count;
			que.push(id);
			g.visit(id);
			count++;
		}
		else
			id=que.front();

		for(int i=0;i<g.numNodes();i++)
		{
			if (g.isEdge(id,i) && i!=que.front())
			{
				if(!g.isVisited(i) && parentCount[id]!=i)
				{
					g.visit(i);
					sf.addEdge(id,i,g.getEdgeWeight(i,id));
					sf.addEdge(i,id,g.getEdgeWeight(i,id));
					que.push(i);
					count++;
					parentCount[id]++;
				}
			}
		}
		que.pop();    
	}

	for (int z=0;z<g.numNodes();z++)
		g.unVisit(z);
}

bool isCyclic(graph &g,int nodeNumber)
// Returns true if the graph g contains a cycle.  Otherwise, returns false.
{
   if (g.isVisited(nodeNumber))
   {
      return true;
   }
   //Visit the node
   g.visit(nodeNumber);
   for (int i=0;i<g.numNodes();i++)
   {
      if (g.isEdge(nodeNumber,i))
      {
         return isCyclic(g,i);
      }
   }

   return false;
}

pqueue getEdges(graph &g)
// iterate through graph and construct a priority queue with minimum cost
// only add an edgepair for edge between marked node and unmarked node
{
    pqueue edges;
    for (int i = 0; i < g.numNodes(); i++)
    {
        g.mark(i);
        
        for (int j = 0; j < g.numNodes(); j++)
        {
            if (g.isMarked(i) && !g.isMarked(j) && g.isEdge(i, j))
            {
                edgepair pair = {i, j, g.getEdgeWeight(i, j)};
                edges.push(pair);
            }
        }
    }
    return edges;
}

void kruskal(graph &g, graph &sf)
// Given a weighted graph g, sets sf equal to a minimum spanning
// forest on g. Uses Kruskal's algorithm.
{
   g.clearMark();
   g.clearVisit();
   numComponents=0;
   while(!g.allNodesVisited())
   {
      // find the smallest edge
      int smallestEdgeWeight = -1;
      int smallestEdgeBeg = -1;
      int smallestEdgeEnd = -1;
      for(int i = 0; i < g.numNodes(); i++)
      {
         for(int j = 0; j < g.numNodes(); j++)
         {
            if(g.isEdge(i, j) && !g.isVisited(i, j) && !g.isVisited(j, i)
               && (!g.isVisited(i) || !g.isVisited(j)))
            {
               if(g.getEdgeWeight(i, j) < smallestEdgeWeight 
                  || smallestEdgeWeight == -1)
               {
                  smallestEdgeWeight = g.getEdgeWeight(i, j);
                  smallestEdgeBeg = i;
                  smallestEdgeEnd = j;
               }
            }
         }
      }
      // add the new edge
      g.visit(smallestEdgeBeg);
      g.visit(smallestEdgeEnd);
      g.visit(smallestEdgeBeg, smallestEdgeEnd);
      sf.addEdge(smallestEdgeBeg, smallestEdgeEnd);
      sf.setEdgeWeight(smallestEdgeBeg, smallestEdgeEnd, smallestEdgeWeight);
   }
   numComponents = getNumComponents(sf);
}

void prim(graph &g, graph &sf)
// Given a weighted graph g, sets sf equal to a minimum spanning
// forest on g. Uses Prim's algorithm.
{
   g.clearMark();
   g.clearVisit();
   numComponents=0;
   int currentNode = 0;
   while(!g.allNodesVisited())
   {
      // find next currentNode
      while(g.isVisited(currentNode) && currentNode < g.numNodes())
      {
         currentNode++;
      }
      g.visit(currentNode);
      int smallestEdgeWeight = -1;
      int smallestEdgeNode = -1;
      // find shortest new edge from currentNode
      for(int i = 0; i < g.numNodes(); i++)
      {
         if(g.isEdge(currentNode, i))
         {
            if(g.getEdgeWeight(currentNode, i) < smallestEdgeWeight 
               || smallestEdgeWeight == -1)
            {
               smallestEdgeWeight = g.getEdgeWeight(currentNode, i);
               smallestEdgeNode = i;
            }
         }
      }
      // add the new edge
      g.visit(smallestEdgeNode);
      sf.addEdge(currentNode, smallestEdgeNode);
      sf.setEdgeWeight(currentNode, smallestEdgeNode, smallestEdgeWeight);
   }
   numComponents = getNumComponents(sf);
}

// Helper Functions
void visitNodes(int start, graph &g)
	// Visit all nodes reachable from the start node
{
	bool found = false;

	// Mark the start node as visited.
	g.visit(start);

	int v = 0;

	// Keep looking for legal moves as long as there are more neighbors
	// to check.
	while (!found && v < g.numNodes())
	{
		// if v is an unvisited neighbor of the start node, recurse.

		if (g.isEdge(start, v) && !g.isVisited(v))
		{
			visitNodes(v, g);
		}
		v++;
	}
} // visitNodes