Wondering if it has something to do with the number being at the start of the word, but that doesn't quite make sense

But that's exactly it ;-) %[] only matches a non-empty sequence of characters. As soon as the match fails, sscanf() returns, without parsing the integer.

You wrong, because string VOWELS is of constant length (5) and does not depend on an input. So it will be O(n*const) = O(n).

me too ;)

also, src == "" does not do what you think it does. In C, use strcmp() to compare strings. Using == compares their addresses in memory

• what are the critical qualities of a C-string?
• also, read the error messages

Your solution is almost good, but it has some problems:

• sometimes, it returns a non-freeable string,
• it does not handle invalid cases correctly (you need to carefully read the description once again).

Your solution is missing some things, it's not a kata issue.