This challenge has a beautiful one-liner answer.

"A hacker practices on HackerRank until getting to a rating of O(1) read as (Oh-one)"

Call the method coder.practice until coder.oh_one? becomes true.

Use the until control structure.

until is the logical equivalent of while not.

Hint

while not <condition>
    <code>
end

or

until <condition>
    <code>
end

or the beautiful one-liner

<code> until <condition>