/// <summary>
/// 构造函数。
/// </summary>
/// <param name="line">所属线路。</param>
/// <param name="from">来源站点。</param>
/// <param name="to">目标站点。</param>
/// <exception cref="ArgumentNullException">如果from或to为空引用，则抛出该异常。</exception>
public MetroLink(MetroLine line, MetroNode from, MetroNode to)
{
if (line == null) throw new ArgumentNullException("line");
if (from == null) throw new ArgumentNullException("from");
if (to == null) throw new ArgumentNullException("to");
m_line = line;
m_from = from;
m_to = to;
}
/// <summary>
/// 获取地铁站点的矩形区域。
/// </summary>
/// <param name="node">地铁站点。</param>
/// <returns></returns>
private Rectangle GetNodeRect(MetroNode node)
{
int r = node.Links.Count > 2 ? 7 : 5;
return new Rectangle(node.X - r, node.Y - r, (r << 1) + 1, (r << 1) + 1);
}
/// <summary>
/// 绘制地铁站点。
/// </summary>
/// <param name="g">绘图图面。</param>
/// <param name="node">地铁站点。</param>
private void PaintNode(Graphics g, MetroNode node)
{
//绘制站点圆圈
Color color = node.Links.Count > 2 ? Color.Black : node.Links[0].Line.Color;
var rect = GetNodeRect(node);
g.FillEllipse(Brushes.White, rect);
using (Pen pen = new Pen(color))
{
g.DrawEllipse(pen, rect);
}
//绘制站点名称
var sz = g.MeasureString(node.Name, this.Font).ToSize();
Point pt = new Point(node.X - sz.Width / 2, node.Y + (rect.Height >> 1) + 4);
g.DrawString(node.Name, Font, Brushes.Black, pt);
}
/// <summary>
/// 查找指定两个节点之间的最短路径。
/// </summary>
/// <param name="startNode">开始节点。</param>
/// <param name="endNode">结束节点。</param>
/// <param name="line">目标线路。</param>
/// <returns>乘车路线列表。</returns>
private List<MetroPath> FindShortestPaths(MetroNode startNode, MetroNode endNode, MetroLine line)
{
List<MetroPath> pathtList = new List<MetroPath>();
if (startNode == endNode) return pathtList;
//路径队列，用于遍历路径
Queue<MetroPath> pathQueue = new Queue<MetroPath>();
pathQueue.Enqueue(new MetroPath());
while (pathQueue.Count > 0)
{
var path = pathQueue.Dequeue();
//如果已经超过最短路径，则直接返回
if (pathtList.Count > 0 && path.Links.Count > pathtList[0].Links.Count)
continue;
//路径的最后一个节点
MetroNode prevNode = path.Links.Count > 0 ? path.Links[path.Links.Count - 1].From : null;
MetroNode lastNode = path.Links.Count > 0 ? path.Links[path.Links.Count - 1].To : startNode;
//继续寻找后续节点
foreach (var link in lastNode.Links.Where(c => c.To != prevNode && (line == null || c.Line == line)))
{
if (link.To == endNode)
{
MetroPath newPath = path.Append(link);
if (pathtList.Count == 0 || newPath.Links.Count == pathtList[0].Links.Count)
{//找到一条路径
pathtList.Add(newPath);
}
else if (newPath.Links.Count < pathtList[0].Links.Count)
{//找到一条更短的路径
pathtList.Clear();
pathtList.Add(newPath);
}
else break;//更长的路径没有意义
}
else if (!path.ContainsNode(link.To))
{
pathQueue.Enqueue(path.Append(link));
}
}
}
return pathtList;
}
/// <summary>
/// 查找一次中转的路线。
/// </summary>
/// <param name="startNode">开始节点。</param>
/// <param name="endNode">结束节点。</param>
/// <returns>乘车路线。</returns>
private MetroPath FindOneTransferPath(MetroNode startNode, MetroNode endNode)
{
List<MetroPath> pathList = new List<MetroPath>();
foreach (var startLine in startNode.Links.Select(c => c.Line).Distinct())
{
foreach (var endLine in endNode.Links.Select(c => c.Line).Where(c=> c != startLine).Distinct())
{
//两条线路的中转站
foreach (var transferNode in this.Graph.GetTransferNodes(startLine, endLine))
{
//起点到中转站的直达路线
var startDirectPathList = FindShortestPaths(startNode, transferNode, startLine);
//中转站到终点的直达路线
var endDirectPathList = FindShortestPaths(transferNode, endNode, endLine);
//合并两条直达路线
foreach (var startDirectPath in startDirectPathList)
{
foreach (var endDirectPath in endDirectPathList)
{
var directPath = startDirectPath.Merge(endDirectPath);
pathList.Add(directPath);
}
}
}
}
}
//挑选最短路线
return GetShortestPath(pathList);
}
/// <summary>
/// 查找直达路线。
/// </summary>
/// <param name="startNode">开始节点。</param>
/// <param name="endNode">结束节点。</param>
/// <returns>乘车路线。</returns>
private MetroPath FindDirectPath(MetroNode startNode, MetroNode endNode)
{
MetroPath path = new MetroPath();
var startLines = startNode.Links.Select(c => c.Line).Distinct().ToList();
var endLines = endNode.Links.Select(c => c.Line).Distinct().ToList();
var lines = startLines.Where(c => endLines.Contains(c)).ToList();
if (lines.Count == 0) return path;
//查找直达路线
List<MetroPath> pathList = new List<MetroPath>();
foreach (var line in lines)
{
pathList.AddRange(FindShortestPaths(startNode, endNode, line));
}
//挑选最短路线
return GetShortestPath(pathList);
}
/// <summary>
/// 查找乘车路线。
/// </summary>
/// <param name="startNode">起点。</param>
/// <param name="endNode">终点。</param>
/// <returns>乘车路线。</returns>
public MetroPath FindPath(MetroNode startNode, MetroNode endNode)
{
MetroPath path = new MetroPath();
if (startNode == null || endNode == null) return path;
if (startNode == endNode) return path;
//如果起点和终点拥有共同线路，则查找直达路线
path = FindDirectPath(startNode, endNode);
if (path.Links.Count > 0) return path;
//如果起点和终点拥有一个共同的换乘站点，则查找一次换乘路线
path = FindOneTransferPath(startNode, endNode);
if (path.Links.Count > 0) return path;
//查找路径最短的乘车路线
var pathList = FindShortestPaths(startNode, endNode, null);
//查找换乘次数最少的一条路线
int minTransfers = int.MaxValue;
foreach (var item in pathList)
{
var curTransfers = item.Transfers;
if (curTransfers < minTransfers)
{
minTransfers = curTransfers;
path = item;
}
}
return path;
}
/// <summary>
/// 判断是否包含指定的站点。
/// </summary>
/// <param name="node">目标站点。</param>
/// <returns></returns>
/// <exception cref="ArgumentNullException">如果node为空引用，则跑出该异常。</exception>
public bool ContainsNode(MetroNode node)
{
if (node == null) throw new ArgumentNullException("node");
return Links.FirstOrDefault(c => c.From == node || c.To == node) != null;
}
