Flat file or plist?

Question

My app requires a list of words for a dictionary. At various stages, the list may be transformed into a binary tree or words sorted by how many characters make up a specified set.
I've started with a flat file of initial words, coincidently sorted alphabetically. However, in the interest of simplicity, my gut feeling says to just go ahead and convert the list into a plist, and then just read it into an NSArray.
Then when it comes to needing a tree structure, to just add use simple indexes into the array in the remaining structured generated in the model portion of the program.
Is that the best way, or would keeping it as a simple flat file keep it simpler?
I'm leaning towards using a plist unless someone talks me out of it, or shows me a few lines of code which read a flat file into an NSArray of NSStrings or equivalent data. By the way, all the words in my dictionaries are all the same length, 5 chars, or 6 chars (each of 2 dictionaries so far). In case I can read n-byte records into a simple dynamic C array in one quick read. I know that would be the tightest memory structure. We have almost 10,000 5 character words and 17,000+ 6 character words.
Only one or the other will be in memory at the same time.

Answer 1

RayNewbie wrote:
The most natural use of a plist is to store a dictionary. Note the seamless interface between NSDictionary and its plist representation in a disk file (see initWithContentsOfFile: and writeToFile:atomically:). So if you already have your data in one or more dictionaries, the job is almost done.
I think I'll go with the plist.
So, the 2nd part of this question is, how to read the data and then pull out the words with unique letters efficiently. I'm sure there are several ways. For ease of programming, I chose to build a dictionary of the letters in the word and if there are N letters in the dictionary for an N letter word, they must be unique.
Actually after an different thread on SQLite, I decided to rewrite it all using NSSet instead of NSDictionary, and now have just 4 tables (NSSet words, NSSet secrets, NSArray allWords, and NSArray allSecrets). The sets are mutable as they are built from potentially multiple data files, although there is only one at the moment, and the arrays which once were mutable can be static, regular NSArrays.
Here's my new code:
//function for unique test
static NSMutableSet* letters = nil;
BOOL uniqueLetters(word)
NSString* word;
if ( !letters ) // first time here, create set
letters = [[NSMutableDictionary alloc] init];
if ( [letters count] ) // been here, want a fresh set, so remove everything
[letters removeAllObjects];
for ( int i = 0; i < [word length]; i++ ) {
NSString* letter = [word substringWithRange:NSMakeRange(i,1)];
[letters addObject:letter];
// if the number of entries in letters == word length there are no duplicates
return ( [letters count] == [word length] );
//loop processing array data in dictionary files to create one list/dictionary
NSArray* myWords = [wordFileData objectForKey:@"Words"];
[words addObjects:myWords]; // add all words from file
for (int i=0; i<[myWords count]; i++) {
NSString* myWord = [myWords objectAtIndex:i];
if ( myWord ) {
// see if it has unique letters so it can be a secret
if ( uniqueLetters(myWord) )
[secrets addObject:myWord]; // list
} // if myword
} // for i
// after processing all files
allWords = [words allObjects]; // all words, no duplicates
allSecrets = [secrets allObjects]; // all secrets, no duplicates