private T GetSmallestContainingIntervalWorker(int start, int length, Func <T, int, int, bool> predicate) { var result = default(T); if (root == null || MaxEndValue(root) < start) { return(result); } var end = start + length; // * our interval tree is a binary tree that is ordered by a start position. // // this method works by // 1. find a sub tree that has biggest "start" position that is smaller than given "start" by going down right side of a tree // 2. once it encounters a right sub tree that it can't go down anymore, move down to left sub tree once and try #1 again // 3. once it gets to the position where it can't find any smaller span (both left and // right sub tree doesn't contain given span) start to check whether current node // contains the given "span" // 4. move up the spin until it finds one that contains the "span" which should be smallest span that contains the given "span" // 5. if it is going up from right side, it make sure to check left side of tree first. using (var pooledObject = SharedPools.Default <Stack <Node> >().GetPooledObject()) { var spineNodes = pooledObject.Object; spineNodes.Push(root); while (spineNodes.Count > 0) { var currentNode = spineNodes.Peek(); // only goes to right if right tree contains given span if (Introspector.GetStart(currentNode.Value) <= start) { var right = currentNode.Right; if (right != null && end < MaxEndValue(right)) { spineNodes.Push(right); continue; } } // right side, sub tree doesn't contain the given span, put current node on // stack, and move down to left sub tree var left = currentNode.Left; if (left != null && end <= MaxEndValue(left)) { spineNodes.Push(left); continue; } // we reached the point, where we can't go down anymore. // now, go back up to find best answer while (spineNodes.Count > 0) { currentNode = spineNodes.Pop(); // check whether current node meets condition if (predicate(currentNode.Value, start, length)) { // hold onto best answer if (EqualityComparer <T> .Default.Equals(result, default) || (Introspector.GetStart(result) <= Introspector.GetStart(currentNode.Value) && Introspector.GetLength(currentNode.Value) < Introspector.GetLength(result))) { result = currentNode.Value; } } // there is no parent, result we currently have is the best answer if (spineNodes.Count == 0) { return(result); } var parentNode = spineNodes.Peek(); // if we are under left side of parent node if (parentNode.Left == currentNode) { // go one level up again continue; } // okay, we are under right side of parent node if (parentNode.Right == currentNode) { // try left side of parent node if it can have better answer if (parentNode.Left != null && end <= MaxEndValue(parentNode.Left)) { // right side tree doesn't have any answer or if the right side has // an answer but left side can have better answer then try left side if (EqualityComparer <T> .Default.Equals(result, default) || Introspector.GetStart(parentNode.Value) == Introspector.GetStart(currentNode.Value)) { // put left as new root, and break out inner loop spineNodes.Push(parentNode.Left); break; } } // no left side, go one more level up continue; } } } return(result); } }