Alot of not needed confusion.

BETWEEN every two blue beads

Thank you for checking out the kata! It seems like you are only downcasing the uppercase vowels. You should additionally upcase the lowercase vowels as well.

Thank you very much

For this kata, unique means that each character is repeated only once.

For example, "abc" is valid, "abca" is not ('a' repeated twice)

1. identify the characters that are repeated onece?
2. Identify the characters that are speacial?

Can someone please explain what is meant by unique characters?

@MAFUS you are the best mate thank you so much. Everything is clear and it makes sense.

Yup to add \0. thanks mate

For both of the allocations you assembled (one in your comment --> malloc and the other in your View Solution --> calloc) you need to review what are the proper expected parameters for those functions to use them correctly, that's all. Hope you get this, best of luck!

Haven't you forgotten something at the end of your string ? ;)

As you know in base 2 all odd numbers has the LSB (Least Significant Bit) set at 1:

0 : 0
1 : 1
2 : 10
3 : 11
4 : 100
5 : 101
[...]

On the other hand the number is given you as a string, aka a character sequence, and the characters are represented in ascii code, thats an integer. In the ascii table the digits representation starts with the 0, then 1, 2, and so on. The ascii code for '0' is 48, so while the digit is even his code is even too. That means I don't need to convert the character to its value to know if the digit is even or odd.

Well, I have an array of sums: sums[0] has the addition of all evens and sums[1] has the addition of all odds. I will use the digit itself to know if it is even or odd:
*digits - I take the digit of the string (his ascii code, remember)
& 1 - I take only his LSB. If it is 1 then the result of the operation is 1; If it is 0 then the result of the operation is 0. I use the result as the index of my array sums.