I've built a trie data structure that looks like this:
struct Trie<Element : Hashable> : Equatable {
private var children: [Element: Trie<Element>]
private var endHere: Bool
}
to perform autocorrection operations on input from a UITextField. I gave the trie a variety of functions such as insert:
/**
Private insert function. Inserts an elements into a trie using a sequences' generator.
- parameter g: `GeneratorType`.
*/
private mutating func insert<G: GeneratorType where G.Element == Element>(g: G) {
var gen = g
if let head = gen.next() {
if case nil = children[head]?.insert(gen) {
children[head] = Trie(g: gen)
}
} else {
endHere = true
}
}
/**
Insert elements into the trie.
- parameter seq: Sequence of elements.
*/
mutating func insert<S: SequenceType where S.Generator.Element == Element>(seq: S) {
insert(seq.generate())
}
the necessary initializers:
/**
Create an empty trie.
*/
init() {
children = [:]
endHere = false
}
/**
Initialize a trie with a generator.
- parameter g: `GeneratorType`.
*/
private init<G: GeneratorType where G.Element == Element>(g: G) {
var gen = g
if let head = gen.next() {
(children, endHere) = ([head:Trie(g: gen)], false)
} else {
(children, endHere) = ([:], true)
}
}
/**
Construct from an arbitrary sequence of sequences with elements of type `Element`.
- parameter s: Sequence of sequences.
*/
init<S: SequenceType, Inner: SequenceType where S.Generator.Element == Inner, Inner.Generator.Element == Element>(_ s: S) {
self.init()
s.forEach { insert($0) }
}
/**
Construct a trie from a sequence of elements.
- parameter s: Sequence.
*/
init <S: SequenceType where S.Generator.Element == Element>(_ s: S) {
self.init(g: s.generate())
}
and conformed Trie to SequenceType so that I can iterate through the elements.
Now, I want to implement a levenshtein distance search where the search function would look like:
func search<S: SequenceType where S.Generator.Element == Element(s: S, maxDistance: Int = 0) -> [(S, Int)] {
}
where the return value is a list of matched subsequences found and max distance it was away from the original query sequence but this is where my knowledge is a bit lacking. I'm not sure how to actually perform the search on my trie and build up a list of matched sequences while calculating the insertion, deletion, and replacement cost.
