public string DLLtoString(DLLnode node)
{
StringBuilder sb = new StringBuilder();
while (node != null)
{
sb.Append(node.val);
node = node.next;
}
return(sb.ToString());
}
public string solution(string S)
{
// deal with special and corner cases
if ((S == null || S == ""))
{
return("");
}
if (S.Length == 1)
{
return(S);
}
if (S.Length == 2)
{
if (S[0] == S[1])
{
return("");
}
else
{
return(S);
}
}
// string length is 3 or more
// Load the string into a Doubly Linked List
//LinkedList<char> list = new LinkedList<char>(S.ToCharArray());
DLLnode list = new DLLnode(S[0]);
list.previous = null;
DLLnode nCurr = list;
DLLnode nNext;
DLLnode nPrev = null;
for (int i = 1; i < S.Length; i++)
{
nNext = new DLLnode(S[i]);
nCurr.next = nNext;
nNext.previous = nCurr;
nCurr = nCurr.next;
}
string transformed = DLLtoString(list);
// Process the Doubly Linked List
nCurr = list;
while (nCurr != null)
{
nNext = nCurr.next;
nPrev = nCurr.previous;
if (nNext == null)
{
break;
}
if (nCurr.val == nNext.val)
{
// take out those two, careful if first or last elements
if (nCurr == list)
{
if (nCurr.next != null)
{
nCurr = nCurr.next.next;
}
list = nCurr;
}
else
{
// 2 elements somewhere in the middle of the list, unlink them
// unlink the current one
nCurr.previous.next = nNext.next;
nCurr = nPrev; // go back 1 node, because the new next might also match
if (nNext.next != null)
{
nNext.next.previous = nCurr; // since nCurr was alread updated
}
}
}
else
{
// nCurr != nNext, keep both and move nCurr up by one
nCurr = nCurr.next;
}
transformed = DLLtoString(list);
}
transformed = DLLtoString(list);
return(transformed);
}