public IList <IList <string> > FindLadders(string beginWord, string endWord, IList <string> wordList)
{
if (!wordList.Contains(endWord))
{
return((IList <IList <string> >) new List <IList <string> >());
}
var infoTree = InfoGraph.GetTreeFrom(beginWord, wordList, endWord, out var endWordIndex, out bool impossibleGetEndWordIndex, out int maxPathValue);
if (impossibleGetEndWordIndex)
{
return((IList <IList <string> >) new List <IList <string> >());
}
return(infoTree.getAllWordPathFromTo(0 /*beginWordIndex*/, endWordIndex, maxPathValue));
}
public static InfoGraph GetTreeFrom(string beginWord, IList <string> wordList, string endWord, out int endWordIndex, out bool impossibleGetEndWordIndex, out int maxPathValue)
{
InfoGraph tree = new InfoGraph(beginWord, wordList);
endWordIndex = 0;
for (; endWordIndex < tree.Infos.Length; endWordIndex++)
{
if (tree.Infos[endWordIndex] == endWord)
{
break;
}
}
if (endWordIndex == tree.Infos.Length)
{
impossibleGetEndWordIndex = true;
maxPathValue = int.MaxValue;
return(null);
}
CreateNearByLetterRelations(tree);
InfoGraph result = GetMinimumPathGraph(tree, 0, endWordIndex, out impossibleGetEndWordIndex, out maxPathValue);
return(result);
}
private static void CreateNearByLetterRelations(InfoGraph infoTree)
{
for (int i = 0; i < infoTree.Infos.Length - 1; i++)
{
for (int j = i + 1; j < infoTree.Infos.Length; j++)
{
if (AreNearByLetter(infoTree.Infos[i], infoTree.Infos[j]))
{
if (infoTree.relations[i] == null)
{
infoTree.relations[i] = new LinkedList <int>();
}
infoTree.relations[i].AddLast(j);
if (infoTree.relations[j] == null)
{
infoTree.relations[j] = new LinkedList <int>();
}
infoTree.relations[j].AddLast(i);
}
}
}
}
private static InfoGraph GetMinimumPathGraph(InfoGraph graph, int beginWordIndex, int endWordIndex, out bool impossibleGetEndWordIndex, out int maxPathValue)
{
impossibleGetEndWordIndex = true;
maxPathValue = int.MaxValue;
MyHeap2 <int, int[]> heap = new MyHeap2 <int, int[]>(graph.Infos.Length);
InfoGraph graphResult = new InfoGraph(graph.Infos);
bool[] selected = new bool[graph.Infos.Length];
int[] pathValues = new int[graph.Infos.Length];
LinkedList <int[]> queue = new LinkedList <int[]>();
selected[beginWordIndex] = true;
queue.AddLast(new int[] { beginWordIndex, -1 });
bool endWordSelected = false;
while (queue.Count != 0)
{
var first = queue.First;
queue.RemoveFirst();
int index = first.Value[0];
pathValues[index] = 1 + first.Value[1];
if (index == endWordIndex)
{
endWordSelected = true;
impossibleGetEndWordIndex = false;
maxPathValue = pathValues[index];
}
if (graph.relations[index] != null)
{
if (graphResult.relations[index] == null)
{
graphResult.relations[index] = new LinkedList <int>();
}
foreach (var item in graph.relations[index])
{
if (endWordSelected)
{
if (item != endWordIndex)
{
continue;
}
else
{
if (pathValues[index] == pathValues[endWordIndex])
{
queue.Clear();
break;
}
}
}
if (!selected[item])
{
selected[item] = true;
queue.AddLast(new int[] { item, pathValues[index] });
}
graphResult.relations[index].AddLast(item);
}
}
}
return(graphResult);
}