I have been playing around a bit with a fairly simple, home-made search engine, and I'm now twiddling with some relevancy sorting code.
It's not very pretty, but I'm not very good when it comes to clever algorithms, so I was hoping I could get some advice :)
Basically, I want each search result to get scoring based on how many words match the search criteria. 3 points per exact word and one point for partial matches
For example, if I search for "winter snow", these would be the results:
Here's the code:
String[] resultWords = result.split(" ");
String[] searchWords = searchStr.split(" ");
int score = 0;
for (String resultWord : resultWords) {
for (String searchWord : searchWords) {
if (resultWord.equalsIgnoreCase(searchWord))
score += 3;
else if (resultWord.toLowerCase().contains(searchWord.toLowerCase()))
score++;
}
}
Basic optimization can be done by preprocessing your database: don't split entries into words every time. Build words list (prefer hash or binary tree to speedup search in the list) for every entry during adding it into DB, remove all too short words, lower case and store this data for further usage.
Linear search is usually very simple to implement, and is practical when the list has only a few elements, or when performing a single search in an un-ordered list. When many values have to be searched in the same list, it often pays to pre-process the list in order to use a faster method.
Your code seems ok to me. I suggest little changes:
Since your are going through all possible combinations you might get the toLowerCase()
of your back at the start.
Also, if an exact match already occurred, you don't need to perform another equals
.
result = result.toLowerCase();
searchStr = searchStr.toLowerCase();
String[] resultWords = result.split(" ");
String[] searchWords = searchStr.split(" ");
int score = 0;
for (String resultWord : resultWords) {
boolean exactMatch = false;
for (String searchWord : searchWords) {
if (!exactMatch && resultWord.equals(searchWord)) {
exactMatch = true;
score += 3;
} else if (resultWord.contains(searchWord))
score++;
}
}
Of course, this is a very basic level. If you are really interested in this area of computer science and want to learn more about implementing search engines start with these terms:
For example, consider this naive score model:
interface ScoreModel {
int startingScore();
int partialMatch();
int exactMatch();
}
...
int search(String result, String searchStr, ScoreModel model) {
String[] resultWords = result.split(" ");
String[] searchWords = searchStr.split(" ");
int score = model.startingScore();
for (String resultWord : resultWords) {
for (String searchWord : searchWords) {
if (resultWord.equalsIgnoreCase(searchWord)) {
score += model.exactMatch();
} else if (resultWord.toLowerCase().contains(searchWord.toLowerCase())) {
score += model.partialMatch();
}
}
}
return score;
}
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