IOS word game. Validate word performance [closed] - ios

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I'm building a scrabble game, and having some problem with the word dictionary. It contains ~700,000 words, and about 18 MB big.
Right now, I'm loading the whole dict into an array, which takes 12 seconds on an iPhone 4.
wordList = [NSMutableArray arrayWithContentsOfFile: [[self applicationDocumentsDirectory] stringByAppendingString:#"/wordlist.plist"]];
I have two questions:
Is there a better way to load the wordlist faster and/or reduce memory?
It takes about 12 seconds to get all possible words from a set of letters. Is it possible to make it quicker? Here's the code:
-(NSMutableArray *)getValidWords:(NSString *)letters{
NSMutableArray *list = [[NSMutableArray alloc] init];
for (int i = 0, c = [wordList count]; i < c; i++){
if ([self isWordValid: [wordList objectAtIndex: i] forLetters:letters]){
[list addObject:[wordList objectAtIndex: i]];
}
}
return list;
}
- (BOOL)isWordValid:(NSString *)word forLetters:(NSString *)ltrs{
int i, z;
NSRange range;
BOOL found;
static NSMutableString *letters = nil;
if ([word length] < 2) return NO;
if(letters == nil) {
letters = [[NSMutableString alloc] initWithString:ltrs];
}
else {
[letters setString: ltrs];
}
found = NO;
range.length = 1;
for(i = 0; i < [word length]; i++){
for(z = 0; z < [letters length]; z++){
if([word characterAtIndex:i] == [letters characterAtIndex:z]){
range.location = z;
[letters deleteCharactersInRange: range];
found = YES;
break;
}
}
if (found == NO){
return NO;
}
found = NO;
}
return YES;
}

Answer 1

You need to change few things to speed up.
Use fast enumeration in place of old C-style loop.
Avoid a lot of method calls.
Use NSPredicate and/or Regex if possible.
As whenever you write [letters length] a method is called, instead of finding it millions of time (this is inside 3rd level of nested loop), store it in a variable and use it.
Fast enumeration : Instead of for(int i=0; i<[someArrays count];i++) use for(id object in someArrays).

Answer 2

Use this
[NSThread detachNewThreadSelector:#selector(fetchWords:) toTarget:self withObject:data];
Do not do it in main thread
use this code modify it if u need to search words
NSMutableArray *subpredicates = [NSMutableArray array];
for(NSString *term in arryOfWordsToBeSearched) {
NSPredicate *p = [NSPredicate predicateWithFormat:#"self contains[cd] %#",term];
[subpredicates addObject:p];
}
NSPredicate *filter = [NSCompoundPredicate andPredicateWithSubpredicates:subpredicates];
result = (NSMutableArray*)[arryOfDummyData filteredArrayUsingPredicate: filter];
//result is a array

Answer 3

Just for starters, create a NSCharacterSet from your letters and call this function before calling the lengthy function. This is a faster check to reduce the possibilities and it should improve your computation time.
NSCharacterSet* lettersSet = [NSCharacterSet characterSetWithCharactersInString:letters];
- (BOOL)isWordValid:(NSString*)word forLettersSet:(NSCharacterSet*)lettersSet {
if ([word length] < 2) return NO;
NSCharacterSet* wordLetters = [NSCharacterSet characterSetWithCharactersInString:word];
return [lettersSet isSupersetOfSet:wordLetters];
}
Ideally, your word database should have precomputed the letter count for each word (e.g. every = {e=2, r=1, v=1, y=1} and your should work only with these structures. Note that the order of letters is not significant - using this fact can greatly improve the performance of your algorithm.
You can also try to create a Core Data database - every word will be one record with a number field for every letter. Then you can create a request which will return you the available words VERY fast.
(Of course, the database will probably take bigger amount of space).
EDIT: Now I have found out NSCountedSet class, so let's try to use it:
-(NSCountedSet*)lettersSetFromString:(NSString*)string {
NSCountedSet* letters = [NSCountedSet set];
[string enumerateSubstringsInRange:NSMakeRange(0, self.length)
options:NSStringEnumerationByComposedCharacterSequences
usingBlock:^(NSString *substring, NSRange substringRange, NSRange enclosingRange, BOOL *stop) {
[letters addObject:substring];
}];
}
-(NSMutableArray *)validWordsForLetters:(NSString*)letters {
NSCountedSet* lettersSet = [self lettersSetFromString:letters];
NSMutableArray* results = [NSMutableArray array];
for (NSString* word in wordList) {
if ([word length] < 2) {
continue;
}
NSCountedSet* wordLettersSet = [self lettersSetFromString:word];
if ([wordLettersSet isSubsetOfSet:lettersSet]) {
[results addObject:word];
}
}
return results;
}
Generating the counted sets for every word beforehand will help the perfomance a lot. Using a Core Data database will still be faster and better for the OS memory.