ios - 如何计算字符串中所有字符的出现次数？

Question

我正在尝试查找字符串中每个字符的使用次数。例如，在字符串“wow”中，我想计算字符“w”的使用次数和字符“o”的使用次数。然后我想将这些字符添加到 NSMutableArray。有没有一种编程方式来计算所有特定字符的使用次数？获取 NSString 中所有字符出现的次数？还是我必须分别计算每个字符出现的次数？

Answer 1

参见 iOS - Most efficient way to find word occurrence count in a string

NSString     *string     = @"wow";
    NSCountedSet *countedSet = [NSCountedSet new];

    [string enumerateSubstringsInRange:NSMakeRange(0, [string length])
                               options:NSStringEnumerationByComposedCharacterSequences | NSStringEnumerationLocalized
                            usingBlock:^(NSString *substring, NSRange substringRange, NSRange enclosingRange, BOOL *stop){

                                // This block is called once for each word in the string.
                                [countedSet addObject:substring];

                                // If you want to ignore case, so that "this" and "This"
                                // are counted the same, use this line instead to convert
                                // each word to lowercase first:
                                // [countedSet addObject:[substring lowercaseString]];
                            }];

    NSLog(@"%@", countedSet);
    NSLog(@"%@", [countedSet allObjects]);
    NSLog(@"%d", [countedSet countForObject:@"w"]);