C#迪杰斯特拉算法

C#迪杰斯特拉算法##

网上有许多版本的，自己还是写一个理解点

Dijkstra.cs

public class Dijkstra
	{
		private List<Node> _nodes;
		private List<Edge> _edges;

		public Dijkstra()
		{
			_nodes = new List<Node>();
			_edges = new List<Edge>();
		}

		public void InitWeights(List<Tuple<string, string, double>> weights)
		{
			_edges = ConvertToEdge(weights);

			InitNodes();
		}

		public List<string> Find(string start, string end)
		{
			var startNode = GetNodeByName(start);
			var endNode = GetNodeByName(end);

			if (startNode == null || endNode == null)
			{
				return new List<string>();
			}

			var s = _nodes.Where(x => x.Name == start).ToList();
			var u = _nodes.Where(x => x.Name != start).ToList();

			s.ForEach(x =>
			{
				x.Weight = 0;
			});

			u.ForEach(x =>
			{
				x.Weight = double.PositiveInfinity;
			});

			while (u.Any())
			{
				var node = s.Last();

				//更新node到x的距离
				u.ForEach(x =>
				{
					var edge = GetEdgeByTwoNode(node, x);

					if (edge != null)
					{
						var weights = node.GetAllWeight() + edge.Weight;

						if (weights < x.Weight)
						{
							x.Weight = weights;
							x.Parent = node;
						}
					}
				});

				//找出距离最小的
				var minNode = u.OrderBy(x => x.Weight).FirstOrDefault();

				s.Add(minNode);
				u.Remove(minNode);
			}

			var paths = new Stack<string>();

			while (endNode != null)
			{
				paths.Push(endNode.Name);
				endNode = endNode.Parent;
			}

			//如果路劲中包含起点
			if (paths.ToList().Contains(start))
			{
				return paths.ToList();
			}
			else
			{
				return new List<string>();
			}
		}

		private Edge GetEdgeByTwoNode(Node start, Node end)
		{
			var edge = _edges.FirstOrDefault(x => x.Start == start.Name && x.End == end.Name);

			if (edge == null)
			{
				edge = _edges.FirstOrDefault(x => x.Start == end.Name && x.End == start.Name);
			}

			return edge;
		}

		/// <summary>
		/// 将权值转换成边
		/// </summary>
		/// <returns></returns>
		private List<Edge> ConvertToEdge(List<Tuple<string, string, double>> weights)
		{
			var edges = new List<Edge>();

			weights.ForEach(weight =>
			{
				edges.Add(new Edge()
				{
					Start = weight.Item1,
					End = weight.Item2,
					Weight = weight.Item3
				});
			});

			return edges;
		}


		/// <summary>
		/// 根据名字获取节点
		/// </summary>
		/// <param name="nodeName"></param>
		/// <returns></returns>
		private Node GetNodeByName(string nodeName)
		{
			return _nodes.FirstOrDefault(x => x.Name == nodeName);
		}

		/// <summary>
		/// 初始化点
		/// </summary>
		private void InitNodes()
		{
			_edges.ForEach(weight =>
			{
				if (_nodes.All(x => x.Name != weight.Start))
				{
					_nodes.Add(new Node()
					{
						Name = weight.Start
					});
				}

				if (_nodes.All(x => x.Name != weight.End))
				{
					_nodes.Add(new Node()
					{
						Name = weight.End
					});
				}
			});
		}
	}

Edge.cs

//表示一条边，从Start到End的权值为多少
	internal class Edge
	{
		public string Start
		{
			get; set;
		}

		public string End
		{
			get; set;
		}

		public double Weight
		{
			get; set;
		}
	}

Node.cs

internal class Node
	{
		public string Name
		{
			get; set;
		}

		public Node Parent
		{
			get; set;
		}

		/// <summary>
		/// 该节点到起点的最短距离
		/// </summary>
		public double Weight
		{
			get; set;
		}

		public double GetAllWeight()
		{
			var allWeight = 0d;

			var node = this;

			do
			{
				allWeight += node.Weight;

				node = node.Parent;

			} while (node != null);

			return allWeight;
		}
	}

使用如下

static void Main(string[] args)
		{
			var weights = new List<Tuple<string, string, double>>()
			{
			new Tuple<string,string,double>("A","B",12),
			new Tuple<string,string,double>("A","F",16),
			new Tuple<string,string,double>("A","G",14),
			new Tuple<string,string,double>("B","F",7),
			new Tuple<string,string,double>("B","C",10),
			new Tuple<string,string,double>("G","F",9),
			new Tuple<string,string,double>("G","E",8),
			new Tuple<string,string,double>("F","C",6),
			new Tuple<string,string,double>("F","E",2),
			new Tuple<string,string,double>("C","D",3),
			new Tuple<string,string,double>("C","E",5),
			new Tuple<string,string,double>("E","D",4),
			};

			var dij = new Dijkstra();

			dij.InitWeights(weights);

			var path = dij.Find("D", "G");

			path.ForEach(Console.WriteLine);
		}