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Closed 10 years ago.
H iguys. I have a loop which parse users id's and adds tham to txt file.
What's the best way than to check if this txt has this id skip it ( while next parsing ).
The size of txt rises from 5-..... mb
I tried to add ids to List, but when the size of file if bigger than 5mb the app begins hanging
Use a HashSet<int> or HashSet<string>, collect the ids in it, then at the end write the result to the text file.
PS: Note that HashSet is O(1) while List is O(n)
You should probably load all of the IDs in the text file into some collection and check if that collection contains the IDs.
I honestly don't think that there's a much more efficient way of doing it than that.
A rule of thumb I believe is to trade time with space. If you want to make copying faster and avoid looking into the file again and again then you may maintain an array or linked list or hash table which also have the id stored in it
var userIsAlreadyThere = File.ReadLines(path).Contains(userid);
Related
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Closed 9 years ago.
I want to make software that groups pictures into folders by date actually taken. The pictures will sort into folders with names the year taken like:
Folder: 2000
Inside the folder: Some pictures taken in the 2000.
How can I do that?
To get the date the picture was actually taken, you want to look at the Exif data.
This data is automatically read into the PropertyItems array when you use Image.FromFile(). You can then use another reference (like this one) to get the right codes for date info. You could also use this library to simplify reading the codes.
Not all images will have Exif data, so you may want to incorporate David's answer as a fallback.
Once you have the relevant date info, you can use Directory.Create(year) and File.Move(oldPath, newPath) to organize the files.
List<string> imageFiles= ... // Here you get the image path
Dictionary<int, List<string>> groupedPaths= ... //output dict
foreach(string str in imageFiles)
{
FileInfo fi=new FileInfo(str);
int year = fi.CreationTime.Year;
if(!groupedPath.ContainsKey(year))
{
var list=new List<string>();
list.Add(year, string);
groupedPaths.Add(year, list);
}
else
{
groupedPaths[year].Add(year, str);
}
//Now you can process with foreach or use LINQ to group your images
foreach(KeyValuePair<int, string> pair in groupedPaths)
{
...
}
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Closed 9 years ago.
It has soon been 12h of trying this and I can't get it to work. I have read all the threads I can find and nothing helps. I have tried to fiddle around with Excel Wrapper as well but it doesn't work. I'm new to C# and I'm trying to do a bullshit generator. What I am trying to do is reading a bunch of words from A1-A5, B1-B5 and C1-C5 in an .xlsx-file and putting them together in a textbox (I'm using Visual Studio) when clicking a button.
If anyone reads this and could give me a hint it would be much appreciated. Thanks in advance.
First you should pull the info from the xls doc to a collection (array, list, etc...)
The code for this should be easy to find online.
You are also going to need a random number generator:
Random rnd = new Random();
Then you are going to have the button click event select 2 random numbers, one for row and one for column, from your collection (2D array in this case):
int row_max = stuff[][].GetLength(0);
int col_max = stuff[][].GetLength(1);
int row = rnd.Next(0, row_max-1)
int col = rnd.Next(0, col_max-1); //between 0 and the number of columns
textbox1.text = textbox1.text + stuff[row][col].ToString();
This is indicative only, but all the parts of this can be easily googled.
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Closed 10 years ago.
I have a field that's stored in the database as a string. It's actually a comma-separated string of numbers that I convert to a list of longs. The lines of code that do the conversion look somewhat like this:
TheListOfLongs = (from string s in StringFromDB.Split(',')
select Convert.ToInt64(s)).ToList<long>();
The code that creates the database storage string looks like this:
return String.Join(",", TheListOfLongs.Select(x=> x.ToString()).ToArray());
This works fine but as you can see, if for some reason there's a problem with the string, the code in the first line of code breaks on Convert.ToInt64(s).
Now I know I can wrap all this around a try statement but my question is this: can storing and retrieving a string in the database corrupt the string (in which case I definitely need the try statement) or is this a one a trillion odd type of event?
I wouldn't worry about corrupt data per se. However, you definitely need to handle the more general case where you can't parse what should be numeric data.
Even in the most controlled situations it is good programming practice to provide conditions for when you can't process data as you're expecting to be able to. What that means to your application is something you'll need to decide. Wrapping the statement with a try..catch will prevent your application from choking, but may not be appropriate if the parsed list is critical later on.
Selecting from the DB shouldn't corrupt your string.
If the connection is dropped mid transfer or something like that then an exception is thrown.
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Closed 10 years ago.
I am looking to generate programmaticaly a list of concrete nouns, an associated picture and if possible a sentence describing the proper noun.
I have tried various dictionary APIs - but the first part of the problem - getting a list of concrete nouns has caused me difficulty. Can anybody think of a good way of achieving this I would be very interested in hearing about it!
Please be aware I know what hashmaps are - and storing this data is not my problem - more sourcing the data is what I need help with - WHERE do I get a list of concrete nouns I can progrmmatically iterate over.
Cheers
NLTK has a part of speech tagger. You could run it on a piece of text and store all the nouns it identifies as your list.
If you want a list of all nouns, you might be in for a long hunt - you'd have to run through every dictionary, encyclopedia, atlas and baby names book in the English language. A more reasonable place to start would be this list of 2336 nouns of various kinds. They reckon it's short of a complete list by 50,000 or so - and my bet is that's an underestimate.
If you want to do in Java
You can use HashMap to store the data; where key can be proper noun and value an object which has other details
HashMap<String, ProperNounObj> obj = new HashMap<String, ProperNounObj>();
where ProperNounObj class has attributes like picutureUrl and description
List of proper noun can be generated by hashmap method obj.keySet(); this will return a set of all proper noun.
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Closed 10 years ago.
I was pleasantly surprised to find how easy it is to use iTextSharp to extract the text from a pdf file. By following this article, I was able to get a pdf file converted to text with this simple code:
string pdfFilename = dlg.FileName;
// Show just the file name, without the path
string pdfFileNameOnly = System.IO.Path.GetFileName(pdfFilename);
lblFunnyMammalsFile.Content = pdfFileNameOnly;
string textFilename = String.Format(#"C:\Scrooge\McDuckbilledPlatypus\{0}.txt", pdfFileNameOnly);
PDFParser pdfParser = new PDFParser();
if (!pdfParser.ExtractText(pdfFilename, textFilename))
{
MessageBox.Show("there was a boo-boo");
}
The problem is that the text file generated contains text like this (i.e. it has no spaces):
IwaspleasantlysurprisedtofindhoweasyitistouseiTextSharptoextractthetextfromatextfile.
Is there an algorithm "out there" that will take text like that and make a best guess as to where the word breaks (AKA "spaces") should go?
Though I agree with Gavin that there's an easy way to solve this problem in this case but the problem itself is an interesting one.
This would require a heuristic algorithm to solve. I will just explain in a bit on why I think so. But first, I'll explain my algorithm.
Store all the dictionary words in a Trie. Now take a sentence, and look up in the trie to get to a word. The trie tracks the end of the word. Once you find a word, add a space to it in your sentence. This will work for your sentence. But consider these two examples:
He gave me this book
He told me a parable
For the first example, the above algorithm works fine but for the second example, the algorithm outputs:
He told me a par able
In order to avoid this, we will need to consider a longest match but if we do that then the output for the first example becomes:
He gave met his book.
So we are stuck and hence add heuristics to the algorithm that will be able to judge that grammatically He gave met his book doesn't make sense.