Finding the most common character in a string

gistfile1.m

- (NSString *)mostCommonCharacter:(NSString *)string
{
    __block NSMutableArray *charIndex = [[NSMutableArray alloc] init];
    
    // Enumerate
    [string enumerateSubstringsInRange:NSMakeRange(0, string.length)  options:NSStringEnumerationByComposedCharacterSequences usingBlock:^(NSString *substring, NSRange substringRange, NSRange enclosingRange, BOOL *stop)
    {
        [charIndex addObject:substring];
    }];
    
    
    // Count
    NSCountedSet *counter = [[NSCountedSet alloc] initWithArray:charIndex];
    NSString *mostCommon;
    NSUInteger highest = 0;
    for (NSString *s in counter) {
        if ([counter countForObject:s] > highest) {
            highest = [counter countForObject:s];
            mostCommon = s;
        }
    }

    return mostCommon;
}


// Demo
- (void)viewDidLoad
{
  NSLog(@"mostCommon: %@", [self mostCommonCharacter:@"aaaabbbaaaa * bbbccccccccdd ddddddd dddd"]);
  // this returns -> d
}