my experience with hackerrank is a company will use hackerrank platform to facilitate the online assessment - NOT look at someone "hacker rank" like you mentioned.

Candidates follows a link a company sent them and gives them an in-browser IDE to solve a problem. The platform records keystrokes, mouse events (like if you left the tab) etc etc. Then when you submit your code it is complied, executed in a sandbox, and tested with test cases. Based on which test cases pass, the execution time and memory usage, hacker rank will generate a report and fwd to the hiring team.

What I was saying in the above comment is if you had the right idea but your code didn't compile or failed the test case, it's as if you failed entirely. No hiring teams sits there and reads the code. Not even garuanteed that an engineer is reviewing your submission.

Hackerrank (to my knowledge) does not parse the code to determine your knowledge of algorithms, data structures, etc etc, it inferes it from which test cases passed and their execution time amd memory usage.