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BkTree.Add

Adds one item, and says whether it was new.

public bool Add(string item)

Parameters — item is the string to index.

Returns — bool: true when the item was added, false when an equal item was already indexed. Matches HashSet<T>.Add.

Example — the second add is refused.

using Lodestar.Text.Indexing;

BkTree tree = BkTree.OverLevenshtein();
bool firstAdd = tree.Add("book");     // => True
bool secondAdd = tree.Add("book");    // => False
int count = tree.Count;               // => 1

Remarks — insertion walks from the root, descending into the child keyed by the distance to the current node and attaching a new node where none exists, so it costs one distance computation per level. A duplicate is detected as a distance of 0, which can only ever be the node itself.

Insertion order decides the tree's shape and therefore how well it prunes; it never decides an answer, which is what the tie-break by insertion rank and the shape-independence test exist for. Adding in sorted order builds a degenerate tree — shuffle a sorted dictionary before indexing it.

Applies to — net10.0, netstandard2.0.

See also — BkTree.AddRange, BkTree.Count.