Creating a suggested words algorithm

I'm designing a cool spell checker (I know I know, modern browsers already have this), anyway, I am wondering what kind of effort would it take to develop a fairly simple but decent suggest-word algorithm.

My idea is that I would first look through the misspelled word's characters and count the amount of characters it matches in each word in the dictionary (sounds resources intensive), and then pick the top 5 matches (so if the misspelled word matches the most characters with 7 words from the dictionary, it will randomly display 5 of those words as suggested spelling).

Obviously to get more advanced, we would look at "common words" and have a dictionary file that is numbered with 'frequency of that word used in English lan开发者_开发技巧guage' ranking. I think that's taking it a bit overboard maybe.

What do you think? Anyone have ideas for this?

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First of all you will have to consider the complexity in finding the "nearer" words to the misspelled word. I see that you are using a dictionary, a hash table perhaps. But this may not be enough. The best and cooler solution here is to go for a TRIE datastructure. The complexity of finding these so called nearer words will take linear order timing and it is very easy to exhaust the tree.

A small example

Take the word "njce". This is a level 1 example where one word is clearly misspelled. The obvious suggestion expected would be nice. The first step is very obvious to see whether this word is present in the dictionary. Using the search function of a TRIE, this could be done O(1) time, similar to a dictionary. The cooler part is finding the suggestions. You would obviously have to exhaust all the words that start with 'a' to 'z' that has words like ajce bjce cjce upto zjce. Now to find the occurences of this type is again linear depending on the character count. You should not carried away by multiplying this number with 26 the length of words. Since TRIE immediately diminishes as the length grows. Coming back to the problem. Once that search is done for which no result was found, you go the next character. Now you would be searching for nace nbce ncce upto nzce. In fact you wont have explore all the combinations as the TRIE data structure by itself will not be having the intermediate characters. Perhaps it will have na ni ne no nu characters and the search space becomes insanely simple. So are the further occurrences. You could develop on this concept further based on second and third order matches. Hope this helped.

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I'm not sure how much of the wheel you're trying to reinvent, so you may want to check out Lucene.

Apache Lucene Core™ (formerly named Lucene Java), our flagship sub-project, provides a Java-based indexing and search implementation, as well as spellchecking, hit highlighting and advanced analysis/tokenization capabilities.