Objective-C: How to find the most common string in an array?

Question

I have an array of strings from an online database that I trying to determine the most commonly used word. The values inside the arrays will vary but I want to check the most co

Answer 1

You can use the word as a key into a dictionary.

NSMutableDictionary *words = [NSMutableDictionary dictionary];
for (NSString *word in stringArray) {
    if (!words[word]) {
        [words setValue:[NSDecimalNumber zero] forKey:word];
    }

    words[word] = [words[word] decimalNumberByAdding:[NSDecimalNumber one]];
}

Now iterate through words and find the key with the highest value.

NSString *mostCommon;
NSDecimalNumber *curMax = [NSDecimalNumber zero];
for (NSString *key in [words allKeys]) {
    if ([words[key] compare:curMax] == NSOrderedDescending) {
        mostCommon = key;
        curMax = word[key];
    }
}

NSLog(@"Most Common Word: %@", mostCommon);

---

EDIT: Rather than looping through the array once then looping separately through the sorted dictionary, I think we can do better and do it all in a single loop.

NSString *mostCommon;
NSDecimalNumber *curMax = [NSDecimalNumber zero];
NSMutableDictionary *words = [NSMutableDictionary dictionary];
for (NSString *word in stringArray) {
    if (!words[word]) {
        [words setValue:[NSDecimalNumber zero] forKey:word];
    }

    words[word] = [words[word] decimalNumberByAdding:[NSDecimalNumber one]];

    if ([words[word] compare:curMax] == NSOrderedDescending) {
        mostCommon = word;
        curMax = words[word];
    }
}

NSLog(@"Most Common Word: %@", mostCommon);

This should be significantly faster than my answer pre-edit, though I don't know how it compares to using the NSCountedSet answer.