public string SearchLevel(BFSNode sourceNode, BFSNode targetNode, ISet <String> validWords)
{
Queue <PathNode> toBeVisited = sourceNode.ToBeVisitedNodes;
while (toBeVisited.Count > 0)
{
PathNode node = toBeVisited.Dequeue();
// Is it visited bottom up?
if (targetNode.VisitedNodes.ContainsKey(node.Word))
{
//Yes.. return the common word;
return(node.Word);
}
// Has it already been visited as a part of the current queue?
IList <string> validNextWords = WordLadderHelper.GetValidLinkedWords(node.Word, validWords);
foreach (string validWord in validNextWords)
{
if (!sourceNode.VisitedNodes.ContainsKey(validWord))
{
PathNode pn = new PathNode(validWord, node);
sourceNode.VisitedNodes.Add(validWord, pn);
sourceNode.ToBeVisitedNodes.Enqueue(pn);
}
}
}
return(null);
}
public IList <string> GetWordLadderPath(string source, string target, ISet <string> validWords)
{
BFSNode sourceNode = new BFSNode(source);
BFSNode targetNode = new BFSNode(target);
while (!sourceNode.IsComplete && !targetNode.IsComplete)
{
string link = SearchLevel(sourceNode, targetNode, validWords);
if (link != null)
{
return(MergePaths(sourceNode, targetNode, link));
}
link = SearchLevel(targetNode, sourceNode, validWords);
if (link != null)
{
var res = MergePaths(sourceNode, targetNode, link);
return(MergePaths(sourceNode, targetNode, link));
}
}
return(null);
}
private IList <string> MergePaths(BFSNode sourceNode, BFSNode destNode, string link)
{
PathNode end1 = sourceNode.VisitedNodes[link];
PathNode end2 = destNode.VisitedNodes[link];
IList <string> list1 = end1.Collapse(false);
IList <string> list2 = end2.Collapse(true);
list2.RemoveAt(0);
for (int i = 0; i < list2.Count; i++)
{
list1.Add(list2[i]);
}
//list2 = null;
return(list1);
}
public IList <IList <string> > GetWordLadderPath2(string source, string target, ISet <string> validWords)
{
BFSNode sourceNode = new BFSNode(source);
BFSNode targetNode = new BFSNode(target);
IList <IList <string> > allShortestpaths = new List <IList <string> >();
HashSet <string> uniqueLinkWords = new HashSet <string>();
//int shortestPathLength = 0;
while (!sourceNode.IsComplete && !targetNode.IsComplete)
{
ISet <string> links = SearchLevel2(sourceNode, targetNode, validWords);
foreach (string link in links)
{
if (!uniqueLinkWords.Contains(link))
{
uniqueLinkWords.Add(link);
var res = MergePaths(sourceNode, targetNode, link);
allShortestpaths.Add(res);
}
}
links = SearchLevel2(targetNode, sourceNode, validWords);
foreach (string link in links)
{
if (!uniqueLinkWords.Contains(link))
{
uniqueLinkWords.Add(link);
var res = MergePaths(sourceNode, targetNode, link);
allShortestpaths.Add(res);
}
}
}
int len = allShortestpaths.Select(x => x.Count).Min();
return(allShortestpaths.Where(x => x.Count == len).ToList());
}