public static Dictionary <int, NodeWeighted> GetTailHeadWeightSpaceGraph(IEnumerable <string> parsed)
{
var nodes = new Dictionary <int, NodeWeighted>();
foreach (var line in parsed)
{
var curArray = line.Split(' ');
var tailNode = int.Parse(curArray[0]);
var headNode = int.Parse(curArray[1]);
var weight = int.Parse(curArray[2]);
if (!nodes.ContainsKey(tailNode))
{
nodes[tailNode] = new NodeWeighted(tailNode);
}
if (!nodes.ContainsKey(headNode))
{
nodes[headNode] = new NodeWeighted(headNode);
}
var neighbourToAdd = new Tuple <NodeWeighted, int>(nodes[headNode], weight);
var parentToAdd = new Tuple <NodeWeighted, int>(nodes[tailNode], weight);
nodes[tailNode].Neighbours.Add(neighbourToAdd);
nodes[headNode].Parents.Add(parentToAdd);
}
return(nodes);
}
public Dictionary <int, NodeWeighted> ReweightEdges(Dictionary <int, NodeWeighted> graph)
{
var lastVertex = graph.Keys.Max();
var newNode = new NodeWeighted(lastVertex + 1);
graph[lastVertex + 1] = newNode;
var parent = new Tuple <NodeWeighted, int>(newNode, 0);
foreach (var vert in graph.Keys)
{
if (vert == lastVertex + 1)
{
continue;
}
graph[vert].Parents.Add(parent);
}
var bellmanResult = new BellmanFord().GetShortestPaths(graph, lastVertex + 1);
if (bellmanResult == null)
{
return(null);
}
var arr = bellmanResult.ToArray();
for (int i = 1; i < lastVertex + 1; i++)
{
if (!arr[i].HasValue)
{
throw new ArgumentException("Some of the shortest paths are null");
}
graph[i].JohnsonsValue = arr[i].Value;
}
graph.Remove(lastVertex + 1);
foreach (var vert in graph.Keys)
{
var vertScore = graph[vert].JohnsonsValue;
for (var i = 0; i < graph[vert].Neighbours.Count; i++)
{
var(neighbour, weight) = graph[vert].Neighbours[i];
var reweighted = weight + vertScore - neighbour.JohnsonsValue;
graph[vert].Neighbours[i] = new Tuple <NodeWeighted, int>(neighbour, reweighted);
}
}
return(graph);
}
// public string Solve()
// {
// var graph = ParseWeightedGraphFromWeb();
//
// var t = new Stopwatch();
// t.Start();
// var pathsArray = new DijkstraShortestPath().GetShortestPaths(graph, 1);
//
// var answerArray = _requiredPaths.Select(x => pathsArray[x]).ToArray();
//
// return string.Join(", ", answerArray);
// }
private Dictionary <int, NodeWeighted> ParseWeightedGraphFromWeb()
{
const string link =
"https://lagunita.stanford.edu/assets/courseware/v1/c8748131579ef6bd10b2d46f616988e9/asset-v1:Engineering+Algorithms1+SelfPaced+type@asset+block/dijkstraData.txt";
var nodes = new Dictionary <int, NodeWeighted>();
var parsed = UtilityMethods.GetParsedStringArrayFromWeb(link, '\n');
var graphArray = new string[parsed.Length][];
for (int i = 0; i < parsed.Length; i++)
{
parsed[i] = parsed[i].Replace("\r", "");
graphArray[i] = parsed[i].Split(new[] { '\t' }, StringSplitOptions.RemoveEmptyEntries);
}
foreach (var stringArray in graphArray)
{
var tailNode = int.Parse(stringArray[0]);
if (!nodes.ContainsKey(tailNode))
{
nodes[tailNode] = new NodeWeighted(tailNode);
}
for (int i = 1; i < stringArray.Length; i++)
{
var temp = stringArray[i].Split(',').Select(int.Parse).ToArray();
var headNode = temp[0];
var weight = temp[1];
if (!nodes.ContainsKey(headNode))
{
nodes[headNode] = new NodeWeighted(headNode);
}
var neighbourToAdd = new Tuple <NodeWeighted, int>(nodes[headNode], weight);
nodes[tailNode].Neighbours.Add(neighbourToAdd);
var parentToAdd = new Tuple <NodeWeighted, int>(nodes[tailNode], weight);
nodes[headNode].Parents.Add(parentToAdd);
}
}
return(nodes);
}
private static Dictionary <int, NodeWeighted> ParseMstGraphFromWeb()
{
const string link =
@"https://lagunita.stanford.edu/assets/courseware/v1/1f93e6cee93cbcf26ee59e2f801646cd/asset-v1:Engineering+Algorithms2+SelfPaced+type@asset+block/edges.txt";
var graphStringsArray = UtilityMethods.GetParsedStringArrayFromWeb(link, '\n');
var nodeCount = int.Parse(graphStringsArray[0].Split(' ')[0]);
var edgeCount = int.Parse(graphStringsArray[0].Split(' ')[1]);
var graph = new Dictionary <int, NodeWeighted>(nodeCount);
for (int i = 1; i <= edgeCount; i++)
{
var currentEdge = graphStringsArray[i].Split(' ').Select(int.Parse).ToArray();
var firstNode = currentEdge[0];
var secondNode = currentEdge[1];
var weight = currentEdge[2];
if (!graph.ContainsKey(firstNode))
{
graph[firstNode] = new NodeWeighted(firstNode);
}
if (!graph.ContainsKey(secondNode))
{
graph[secondNode] = new NodeWeighted(secondNode);
}
var first = graph[firstNode];
var second = graph[secondNode];
first.Neighbours.Add(new Tuple <NodeWeighted, int>(second, weight));
second.Neighbours.Add(new Tuple <NodeWeighted, int>(first, weight));
}
return(graph);
}
