/// <summary>
/// 读取最短路径
/// </summary>
/// <param name="path">路径</param>
/// <param name="start">开始</param>
/// <param name="end">结束</param>
public void GetShortest(ref List <T> path, T start, T end)
{
if (end == null)
{
return;
}
WeightedGraphNode <T> nodeEnd = NodeList.FirstOrDefault(s => s.Data.CompareTo(end) == 0);
Dictionary <T, double> children = nodeEnd.Children;
path.Add(end);
if (children != null)
{
var minData = default(T);
foreach (var itemC in children)
{
WeightedGraphNode <T> nodeC = NodeList.FirstOrDefault(s => s.Data.CompareTo(itemC.Key) == 0);
if ((nodeEnd.Weight - itemC.Value).CompareTo(nodeC.Weight) == 0)
{
minData = nodeC.Data;
break;
}
}
GetShortest(ref path, start, minData);
}
}
/// <summary>
/// 狄克斯特拉算法
/// 如果图中含有负数权重，狄克斯特拉算法可能会无法得出正确答案
/// </summary>
public void Dijkstra(T current, T end)
{
if (NodeList == null)
{
//图为空
return;
}
if (current.CompareTo(end) == 0)
{
return;
}
WeightedGraphNode <T> nodeCurrent = NodeList.FirstOrDefault(s => s.Data.CompareTo(current) == 0);
if (nodeCurrent == null)
{
return;
}
nodeCurrent.Visited = true;
Dictionary <T, double> children = nodeCurrent.Children;
if (children != null)
{
foreach (var itemC in children)
{
WeightedGraphNode <T> nodeChildren = NodeList.FirstOrDefault(s => s.Data.CompareTo(itemC.Key) == 0);
if (nodeChildren.Visited)
{
continue;
}
var currentWeight = nodeCurrent.Weight + itemC.Value;
if (currentWeight.CompareTo(nodeChildren.Weight) < 0)
{
nodeChildren.Weight = currentWeight;
}
BackupList.Add(nodeChildren);
}
}
var minData = default(T);
if (BackupList.Count > 0)
{
double weight = double.MaxValue;
foreach (var backup in BackupList)
{
if (backup.Weight < weight)
{
weight = backup.Weight;
minData = backup.Data;
}
}
}
WeightedGraphNode <T> nodeMin = NodeList.FirstOrDefault(s => s.Data.CompareTo(minData) == 0);
BackupList.Remove(nodeMin);
Dijkstra(minData, end);
}
/// <summary>
/// 贝尔曼-福特算法
/// </summary>
public void BellmanFord()
{
if (NodeList == null)
{
//图为空
return;
}
UpdateNum++;
if (UpdateNum >= NodeList.Count)
{
//该图有负权回路
return;
}
foreach (var node in NodeList)
{
if (!IsWeightChange)
{
return;
}
Dictionary <T, double> children = node.Children;
if (children != null)
{
foreach (var itemC in children)
{
WeightedGraphNode <T> nodeChildren = NodeList.FirstOrDefault(s => s.Data.CompareTo(itemC.Key) == 0);
var currentWeight = node.Weight + itemC.Value;
if (currentWeight.CompareTo(nodeChildren.Weight) < 0)
{
nodeChildren.Weight = currentWeight;
IsWeightChange = true;
}
else
{
IsWeightChange = false;
}
}
}
}
BellmanFord();
}
