ios - Efficent way to sort 'Person.firstName' under first alphabetically letter -

i iterate through long list of names, assign each 'person' object. person object has firstname , lastname. looking efficent way sort firstnames beginning letter a through z. have come solutions not efficent, or there surely easier way creating '24' arrays each letter of alphabet.

 for(int = 0; < numberofpeople; i++) {      ...      if ([person.firstname hasprefix:@"a"] || [person.firstname hasprefix:@"a"]) {             [self.lettera_array addobject:person];//nsmutablearray          }      ...   } 

i similar below example if work objects, unsure:

nsdictionary *animals = @{@"b" : @[@"bear", @"black swan", @"buffalo"],             @"c" : @[@"camel", @"cockatoo"],             @"d" : @[@"dog", @"donkey"],             @"e" : @[@"emu"],             @"g" : @[@"giraffe", @"greater rhea"],             @"h" : @[@"hippopotamus", @"horse"],             @"k" : @[@"koala"],             @"l" : @[@"lion", @"llama"],             @"m" : @[@"manatus", @"meerkat"],             @"p" : @[@"panda", @"peacock", @"pig", @"platypus", @"polar bear"],             @"r" : @[@"rhinoceros"],             @"s" : @[@"seagull"],             @"t" : @[@"tasmania devil"],             @"w" : @[@"whale", @"whale shark", @"wombat"]}; 

you this:

nsarray *names = @[@"bob", @"book2", @"august", @"zulu", @"agnoz"]; nsmutabledictionary *buckets = [[nsmutabledictionary alloc] init]; (nsstring *name in names) {     nsstring *index = [name substringtoindex:1];     if (!buckets[index]) {         buckets[index] = [[nsmutablearray alloc] init];     }     [buckets[index] addobject:name]; }