How to correct the user input (Kind of google “did you mean?”)

Question

I have the following requirement: -

I have many (say 1 million) values (names). The user will type a search string.

I don\'t expect the user to spell the names c

Answer 1

For people who are recommending Soundex, it is very out of date. Metaphone (simpler) or Double Metaphone (complex) are much better. If it really is name data, it should work fine, if the names are European-ish in origin, or at least phonetic.

As for the search, if you care to roll your own, rather than use Aspell or some other smart data structure... pre-calculating possible matches is O(n^2), in the naive case, but we know in order to be matching at all, they have to have a "phoneme" overlap, or may even two. This pre-indexing step (which has a low false positive rate) can take down the complexity a lot (to in the practical case, something like O(30^2 * k^2), where k is << n).