Dubious because:

• it is not clear that recursion is that much inefficient when using a logarithmic algorithm like here, moreover the resulting code is much lighter and much more readable;
• You seem to forget that your code is compiled and the compiler knows very well how to optimize this kind of trivial operations, so it is more than reasonable to assume it will choose the most efficient method, no matter if you use bitwise or classical division initially.

While this solution might look cleaner it has an O(nlog(n)) time complexity in the best case.
This could easy have an linear time complexity using a hash-map.

why long?

clever!!
but ineffiecient due to:-

1. Recursive;
2. Using arithmatic logic instead to bitwise;

you should really make an array for counting repeats (i.e. frequence array or ans unordered map);

wow! I didn't knew you could use end[-1] insted of *(end - 1) as well;
THANK YOU!