private IEnumerable <GraphNode> SolveGraph(Dictionary <string, Dictionary <string, int> > graph)
{
GraphNode path = null;
var open = new HashSetOrderedBy <GraphNode, int>((state) => state.Cost);
var close = new HashSet <GraphNode>();
var keyToHash = new Dictionary <string, int>();
var hash = 1;
foreach (var key in graph.Keys)
{
keyToHash.Add(key, hash);
hash <<= 1;
}
var locationsToVisit = hash - 1;
foreach (var location in graph.Keys)
{
var initState = new GraphNode
{
CurrentPos = location,
LocationsToVisit = locationsToVisit - keyToHash[location],
Cost = 0,
};
open.Add(initState);
}
while (open.Any())
{
var currentNode = open.ValueWithMinSelector();
var children = this.GenerateChildren(currentNode, graph, path, keyToHash);
foreach (var child in children)
{
if (open.TryGetValue(child, out GraphNode existingNode) || close.TryGetValue(child, out existingNode))
{
if (existingNode.Cost <= child.Cost)
{
continue;
}
open.Remove(existingNode);
}
open.Add(child);
if (child.LocationsToVisit == 0)
{
path = child;
var nodesToDelete = open.Where(n => n.Cost >= path.Cost).ToList();
foreach (var nd in nodesToDelete)
{
open.Remove(nd);
}
}
}
open.Remove(currentNode);
close.Add(currentNode);
yield return(currentNode);
}
yield return(path);
}
private IEnumerable <GraphNode> GenerateChildren(GraphNode currentNode, Dictionary <string, Dictionary <string, int> > graph, GraphNode path, Dictionary <string, int> keyToHash)
{
foreach (var kvp in graph[currentNode.CurrentPos])
{
if ((currentNode.LocationsToVisit & keyToHash[kvp.Key]) == 0)
{
continue;
}
var h = currentNode.Cost + kvp.Value;
if (path != null && path.Cost < h)
{
continue;
}
yield return(new GraphNode
{
CurrentPos = kvp.Key,
Cost = h,
LocationsToVisit = currentNode.LocationsToVisit - keyToHash[kvp.Key],
Parent = currentNode,
});
}
}
private IEnumerable <GraphNode> TSP(Dictionary <string, Dictionary <string, int> > graph, HashSet <string> visited, GraphNode currPos, int n, int count, GraphNode ans)
{
if (count == n)
{
if (ans.Cost < currPos.Cost)
{
ans.Parent = currPos.Parent;
ans.Cost = currPos.Cost;
ans.CurrentPos = currPos.CurrentPos;
}
yield break;
}
if (currPos == null)
{
foreach (var nextLocation in graph.Keys)
{
visited.Add(nextLocation);
var next = new GraphNode
{
Parent = currPos,
Cost = 0,
CurrentPos = nextLocation,
};
foreach (var innerNodes in this.TSP(graph, visited, next, n, count + 1, ans))
{
yield return(innerNodes);
}
visited.Remove(nextLocation);
}
}
else
{
foreach (var nextLocation in graph[currPos.CurrentPos].Keys)
{
if (!visited.Contains(nextLocation))
{
visited.Add(nextLocation);
var next = new GraphNode
{
Parent = currPos,
Cost = currPos.Cost + graph[currPos.CurrentPos][nextLocation],
CurrentPos = nextLocation,
};
yield return(next);
foreach (var innerNodes in this.TSP(graph, visited, next, n, count + 1, ans))
{
yield return(innerNodes);
}
visited.Remove(nextLocation);
}
}
}
}
