private List <IList <string> > GetRes(MultiLink <string> start)
{
List <IList <string> > res = new List <IList <string> >();
if (start.pre.Count == 0)
{
res.Add(new List <string>());
res[0].Add(start.val);
return(res);
}
foreach (MultiLink <string> temp in start.pre)
{
List <IList <string> > last = GetRes(temp);
foreach (IList <string> templist in last)
{
List <string> toadd = new List <string>(templist);
toadd.Add(start.val);
res.Add(toadd);
}
}
return(res);
}
public IList <IList <string> > FindLadders(string beginWord, string endWord, IList <string> wordList)
{
HashSet <string> set = new HashSet <string>(wordList);
if (set.Contains(beginWord))
{
set.Remove(beginWord);
}
if (!set.Contains(endWord))
{
return(new List <IList <string> >());
}
List <List <MultiLink <string> > > bfs = new List <List <MultiLink <string> > >();
bfs.Add(new List <MultiLink <string> >());
bfs[0].Add(new MultiLink <string>(beginWord));
Dictionary <string, int> curentlevel = new Dictionary <string, int>();
bool tobreak = false;
while (set.Count != 0)
{
int recordSetCount = set.Count;
bfs.Add(new List <MultiLink <string> >());
foreach (MultiLink <string> mltemp in bfs[bfs.Count - 2])
{
string word = mltemp.val;
for (int i = 0; i < word.Length; i++)
{
char[] wordunit = word.ToCharArray();
for (char j = 'a'; j <= 'z'; j++)
{
wordunit[i] = j;
string tempstr = new string(wordunit);
if (set.Contains(tempstr))
{
if (!curentlevel.ContainsKey(tempstr))
{
curentlevel.Add(tempstr, bfs.Last().Count);
bfs.Last().Add(new MultiLink <string>(tempstr));
}
bfs.Last()[curentlevel[tempstr]].AddPre(mltemp);
if (tempstr == endWord)
{
tobreak = true;
}
}
}
}
}
if (tobreak)
{
break;
}
foreach (string toRemove in curentlevel.Keys)
{
set.Remove(toRemove);
}
if (set.Count == recordSetCount)
{
return(new List <IList <string> >());
}
curentlevel.Clear();
}
MultiLink <string> start = bfs.Last()[curentlevel[endWord]];
return(GetRes(start));
}
public void AddPre(MultiLink <T> newpre)
{
pre.Add(newpre);
}