public Trie(IEnumerable <string> strings)
{
// O(m^2 * n)
// n is a number of strings
// m is a max length
var root = new NodeString("");
var eow = new NodeString(".");
foreach (var str in strings)
{
var node = root;
foreach (var ch in str)
{
var next = node.Children.FirstOrDefault(n => n.Value == ch.ToString());
if (next == null)
{
next = new NodeString(ch.ToString());
node.Children.Add(next);
}
node = next;
}
node.Children.Add(eow);
}
Root = root;
}
private static void Shrink(NodeString item)
{
while (item.Children.Count == 1)
{
var child = item.Children[0];
item.Value += child.Value;
item.Children = child.Children;
}
}
public void Insert(string s)
{
// O(m*n)
// TODO: it is not working with non-empty root
var inode = Root;
var istr = s + ".";
while (true)
{
var isGoDeeper = false;
foreach (var child in inode.Children)
{
var common = istr.CommonPrefix(child.Value);
if (common.Length == child.Value.Length)
{
inode = child;
istr = istr.Substring(common.Length);
isGoDeeper = true;
break; // Go deeper one level
}
if (common.Length > 0)
{
var remExisting = new NodeString(child.Value.Substring(common.Length))
{
Children = child.Children
};
var remInserting = new NodeString(istr.Substring(common.Length));
var commonNode = new NodeString(common);
inode.Children.Remove(child);
inode.Children.Add(commonNode);
commonNode.Children.Add(remExisting);
commonNode.Children.Add(remInserting);
return; // Finish inserting
}
}
if (!isGoDeeper)
{
// No child with appropriate prefix found
inode.Children.Add(new NodeString(istr));
return;
}
}
}
private static NodeString ConvertTrieToRadix(NodeString root)
{
// O(m*n)
var queue = new Queue <NodeString>();
queue.Enqueue(root);
while (queue.Count > 0)
{
var item = queue.Dequeue();
Shrink(item);
foreach (var child in item.Children)
{
queue.Enqueue(child);
}
}
return(root);
}
public Radix(IEnumerable <string> strings)
{
var trie = new Trie(strings);
Root = ConvertTrieToRadix(trie.Root);
}