I want to compare two strings, such as:
str1 = "this is a dynamic data";
str2 = "this is a <data_1> data";
Is there any method that will find the nearest match? I have used Ternary Search Tree (TST) Dictionary functions. Are there any other ways to do this kind of thing?
What about the Jaccard similarity coefficient?
http://en.wikipedia.org/wiki/Jaccard_index
It's easy to implement and gives a good similarity score. You have to tokenize your sentences though ;)
There is no such method in BCL that finds nearest match of the string.
But you can roll your own.
read about "Levenshtein Distance" on the following link
In am not sure about this thing in C#, but yes that is there in SQL,
select difference('this is a dynamic data','this is a dynamic')
Related
I'm working of filtering comments. I'd like to replace string like this:
llllolllllllllllooooooooooooouuuuuuuuuuuddddddddddddddllllollllllllllllloooooooooooooooooouuuuuuuuuuuuuuuuuuddddddddddddddllllollllllllllllloooooooooooooooooouuuuuuuuuuuuuuuuuuddddddddddddddllllollllllllllllloooooooooooouuuuuuuuuuuuuuuuudddddddddddddd
with two words: lol loud
string like this:
cuytwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwww
with: cuytw
And string like this:
hyyuyuyuyuyuyuyuyuyuyuyuyuyu
with: hyu
but not modify strings like look, geek.
Is there any way to achieve this with single regular expression in C#?
I think I can answer this categorically.
This definitely cant be done with RegEx or even standard code due to your input and output requirements without at minimum some sort of dictionary and algorithm to try and reduce doubles in a permutation check for legitimate words.
The result (at best) would give you a list of possible non mutually-exclusive combinations of nonsense words and legitimate words with doubles.
In fact, I'd go as far to say with your current requirements and no extra specificity on rules, your input and output are generically impossible and could only be taken at face value for the cases you have given.
I'm not sure how to use RegEx for this problem, but here is an alternative which is arguably easier to read.*
Assuming you just want to return a string comprising the distinct letters of the input in order, you can use GroupBy:
private static string filterString(string input)
{
var groups = input.GroupBy(c => c);
var output = new string(groups.Select(g => g.Key).ToArray());
return output;
}
Passes:
Returns loud for llllolllllllllllooooooooooooouuuuuuuuuuuddddddddddddddllllollllllllllllloooooooooooooooooouuuuuuuuuuuuuuuuuuddddddddddddddllllollllllllllllloooooooooooooooooouuuuuuuuuuuuuuuuuuddddddddddddddllllollllllllllllloooooooooooouuuuuuuuuuuuuuuuudddddddddddddd
Returns cuytw for cuytwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwww
Returns hyu for hyyuyuyuyuyuyuyuyuyuyuyuyuyu
Failures:
Returns lok for look
Returns gek for geek
* On second read you want to leave words like look and geek alone; this is a partial answer.
How do i Evaluate the following expression from a string to a answer as an integer?
Expression:
√(7+74) + √(30+6)
Do i have to evaluate each one of the parameters like Sqroot(7+74) and Sqroot(30+6) or is it possible to evaluate the whole expression. Any ideas?
If this string is user-supplied (or anyway available only at runtime) what you need is a mathematical expressions parser (maybe replacing the √ character in the text with sqrt or whatever the parser likes before feeding the string to it). There are many free ones available on the net, personally I used info.lundin.math several times without any problem.
Quick example for your problem:
info.lundin.Math.ExpressionParser parser = new info.lundin.Math.ExpressionParser();
double result = parser.Parse("sqrt(7+74)+sqrt(30+6)", null);
(on the site you can find more complex examples with e.g. parameters that can be specified programmatically)
You can use NCalc for this purpose
NCalc.Expression expr = new NCalc.Expression("Sqrt(7+74) + Sqrt(30+6)");
object result = expr.Evaluate();
Is it possible somehow to do a RegEx-replace with a calculation in the result? (in VS2010)
Such as:
Grid\.Row\=\"{[0-9]+}\"
to
Grid.Row="eval(int(\1) + 1)"
You can use a MatchEvaluator do achieve this, like
String s = Regex.Replace("1239", #"\d", m => (Int32.Parse(m.ToString()) + 1).ToString());
Output: 23410
Edit:
I just noticed... if you mean "using the VS2010 find-replace feature" and not "using C#", then the answer is "no", i am afraid.
You could always use capturing to retrieve any values you need for your calculation and then perform a RegEx Replace with a new RegEx that's constructed from you're equation and any values you captured.
If the equation doesn't use anything from the input text, one RegEx would be sufficient. You'd simply construct it by concatenating the static portions together with the computed value(s).
Unfortunately, C# and .NET do not provide an eval method or equivalent. However, it is possible to either use a library for expression parsing (a quick google gave me this .NET Math Expression Parser) or write your own (which is actually pretty easy, check out the Shunting-yard Algorithm and Postfix Notation). Simply capture the group then output the group value to the library/method you have written.
Edit: I see now you want this for the VS2010 program. This is unachievable unless you write your own VS extension. You could always write a program to search and replace your code and feed the code into it, then replace it the original code with its output.
for example i'd need to create something like google search query parser to parse such expressions as:
flying hiking or swiming
-"**walking in boots **" **author:**hamish **author:**reid
or
house in new york priced over
$500000 with a swimming pool
how would i even go about start building something like it? any good resources?
c# relevant, please (if possible)
edit: this is something that i should somehow be able to translate to a sql query
How many keywords do you have (like 'or', 'in', 'priced over', 'with a')? If you only have a couple of them I'd suggest going with simple string processing (regexes) too.
But if you have more than that you might want to look into implementing a real parser for those search expressions. Irony.net might help you with that (I found it extremely easy to use as you can express your grammar in a near bnf-form directly in code).
The Lucene/NLucene project have functionality for boolean queries and some other query formats as well. I don't know about the possibilities to add own extensions like author in your case, but it might be worthwile to check it out.
There are few ways doing it, two of them:
Parsing using grammar (useful for complex language)
Parsing using regular expression and basic string manipulations (for simpler language)
According to your example, the language is very basic so splitting the string according to keyword can be the best solution.
string sentence = "house in new york priced over $500000 with a swimming pool";
string[] values = sentence.Split(new []{" in ", " priced over ", " with a "},
StringSplitOptions.None);
string type = values[0];
string area = values[1];
string price = values[2];
string accessories = values[3];
However, some issues that may arise are: how to verify if the sentence stands in the expected form? What happens if some of the keywords can appear as part of the values?
If this is the case you encounter there are some libraries you can use to parse input using a defined grammar. Two of these libraries that works with .Net are ANTLR and Gold Parser, both are free. The main challenge is defining the grammar.
A grammar would work very well for the second example you gave but the first (any order keyword/command strings) would be best handled using Split() and a class to handle the various keywords and commands. You will have to do initial processing to handle quoted regions before the split (for example replacing spaces within quoted regions with a rare/unused character).
The ":" commands are easy to find and pull out of the search string for processing after the split is completed. Simply traverse the array looking.
The +/- keywords are also easy to find and add to the sql query as AND/AND NOT clauses.
The only place you might run into issues is with the "or" since you'll have to define how it is handled. What if there are multiple "or"s? But the order of keywords in the array is the same as in the query so that won't be an issue.
i think you should just do some string processing. There is no smart way of doing this.
So replace "OR" with your own or operator (e.g. ||). As far as i know there is no library for this.
I suggest you go with regexes.
I'd like to figure out (in runtime) whether or not two regular expressions intersect (i.e. if they do there exist one or more string the matches both regular expressions).
Algorithm needs to be pretty fast as I need to loop through a database and check existing values.
Found some theory on this but no implementations?
The obvious solution would be to convert the regexes to DFAs, compute the intersection of the DFAs (trivial) and see if there's anything the resulting DFA can accept (also trivial). The only hard part is converting the regexes to DFAs, which requires some work.
Here's an implementation in Haskell using partial derivatives of regexps. A comment to that post points out an issue with the approach in Chris Dodd's answer.
What about checking first one and then the other with the input that passed the first?