void _buildTree(string[] keywords)
{
//build keyword tree and transition function
_root = new InnerNode(null, ' ');
var keywordCount = keywords.Length;
for (int i = 0; i < keywordCount; ++i)
{
var p = keywords[i];
// add pattern to tree
InnerNode nd = _root;
foreach (var c in p)
{
InnerNode ndNew = null;
foreach (InnerNode trans in nd._transitionsArr)
{
if (trans._char == c)
{
ndNew = trans; break;
}
}
if (ndNew == null)
{
ndNew = new InnerNode(nd, c);
nd.AddTransition(ndNew);
}
nd = ndNew;
}
nd.AddResult(p, i);
}
// Find failure functions
var nodes = new List <InnerNode>();
// level 1 nodes - fail to root node
foreach (InnerNode nd in _root._transitionsArr)
{
nd._failure = _root;
foreach (InnerNode trans in nd._transitionsArr)
{
nodes.Add(trans);
}
}
// other nodes - using BFS
while (nodes.Count != 0)
{
var newNodes = new List <InnerNode>();
foreach (InnerNode nd in nodes)
{
InnerNode r = nd._parent._failure;
char c = nd._char;
while (r != null && !r.ContainsTransition(c))
{
r = r._failure;
}
if (r == null)
{
nd._failure = _root;
}
else
{
nd._failure = r.GetTransition(c);
foreach (var result in nd._failure._results)
{
nd.AddResult(result.Key, result.Value);
}
}
// add child nodes to BFS list
foreach (InnerNode child in nd._transitionsArr)
{
newNodes.Add(child);
}
}
nodes = newNodes;
}
_root._failure = _root;
}