optimize(2109): adding spaces to a string

[massivebird]

Challenge

I peeked at the better solutions. They turn the input string into bytes, iterate through the strictly-increasing collection of space indices, and do byte(?)-wise copying accordingly.

My question: is this low-level copying that much better than my high-level iterative approach? Or is there some finer optimization happening? (I think it really is simply better)

[massivebird]

This StackOverflow post has a helpful comment in it!

Since Rust is designed to support UTF-8 which supports variable-length characters, the .chars() iterator must compute the length of the next character before returning it. On the other hand, .as_bytes() just iterates by a fixed amount every time with less additional computation.

Definitely part of the problem!