public SearchResult AStarSearch(IHeuristic heuristic)
{
NodeComparator comparator = (node1, node2) => node1.FHat.CompareTo(node2.FHat);
return(GenericSearch(_initialState, _goalState, "AStar",
comparator, (state1, state2) => 1, heuristic));
}
public SearchResult GreedyBestFirstSearch(IHeuristic heuristic)
{
NodeComparator comparator = (node1, node2) => node1.HHat.CompareTo(node2.HHat);
return(GenericSearch(_initialState, _goalState, "Greedy Best First Search",
comparator, (state1, state2) => 1, heuristic));
}
public SearchResult UCS()
{
NodeComparator comparator = (node1, node2) => node1.GHat.CompareTo(node2.GHat);
CostFunc cost = (state1, state2) => 1;
return(GenericSearch(_initialState, _goalState, "UCS", comparator, cost, null));
}
public SearchResult DFS(int depthLimit)
{
string name = "DFS (DepthLimit: " + depthLimit + ")";
NodeComparator comparator = (node1, node2) => (-node1.Depth).CompareTo(-node2.Depth);
return(GenericSearch(_initialState, _goalState, name, comparator, (state1, state2) => 1, null, depthLimit));
}
public Frontier(NodeComparator compareNodes)
{
_compareNodes = compareNodes;
_hashByState = new Dictionary <StateBase, List <Node> >();
_pQueue = new SortedList <Key, List <Node> >();
}
public Key(Node node, NodeComparator comparator)
{
_node = node;
_compareNodes = comparator;
}
public SearchResult GenericSearch(StateBase initialState,
StateBase goalState,
string algName,
NodeComparator comparator,
CostFunc cost,
IHeuristic heuristic,
int?depthLimit = null)
{
Frontier frontier = new Frontier(comparator);
Explored explored = new Explored();
HeuristicCache cache = new HeuristicCache(goalState, heuristic);
int nodesGenerated = 0;
int nodesPrevGenerated = 0;
Node initNode = new Node(initialState, cost, null, null, cache.Evaluate);
frontier.Push(initNode);
while (true)
{
if (frontier.Count == 0)
{
return(new SearchResult(null, nodesGenerated, nodesPrevGenerated, 0, explored.Count, algName, heuristic));
}
Node node = frontier.Pop();
explored.Push(node);
// goal test
if (node.State.Equals(goalState))
{
return(new SearchResult(node, nodesGenerated, nodesPrevGenerated, frontier.Count, explored.Count, algName, heuristic));
}
if (depthLimit != null && node.Depth == depthLimit)
{
continue;
}
IEnumerable <Node> children = node.Successors(cost, cache.Evaluate);
foreach (Node child in children)
{
nodesGenerated++;
// If this state is found in the Frontier, replace the old state with the new state if its GHat is smaller
Node foundInFrontier = frontier.Find(child.State);
if (foundInFrontier != null)
{
nodesPrevGenerated++;
if (foundInFrontier.GHat > child.GHat)
{
frontier.Replace(foundInFrontier, child);
}
}
else
{
Node foundInExplored = explored.Find(child.State);
// If this state is found in the Explored, replace the old state with the new state if its GHat is smaller
if (foundInExplored != null)
{
nodesPrevGenerated++;
if (foundInExplored.GHat > child.GHat)
{
explored.Remove(foundInExplored);
frontier.Push(child);
}
}
else
{
// doesn't exist in frontier or explored, adding to frontier.
frontier.Push(child);
}
}
}
}
}
public SearchResult BFS()
{
NodeComparator comparator = (node1, node2) => node1.Depth.CompareTo(node2.Depth);
return(GenericSearch(_initialState, _goalState, "BFS", comparator, (state1, state2) => 1, null));
}
