applied for a senior frontend/mobile role at Samsung, went through their online assessment last month. sharing format and difficulty because the info online is mostly outdated (2022-era posts about a different OA platform).
platform: HackerRank. 90 minutes, 2 coding problems. no proctoring camera in my case, just screen share.
difficulty: problem 1 was medium-ish. sliding window on a string, fairly standard. i'd call it easy-medium. problem 2 was harder: a graph traversal problem on a grid with some state to track. not impossible but required getting the state representation right, which ate time.
i finished both but problem 2 solution was O(n^3) and i suspected it wouldn't pass all test cases. ended up getting partial credit on that one.
things i noticed: test cases were visible for problem 1, hidden for problem 2. always write for edge cases you can't see. time limit was strict. i had maybe 3 minutes left after finishing. don't dawdle on approach, commit and iterate. language options: Java, Python, C++, JavaScript, a few others. i used Python.
outcome: moved to phone screen, so partial credit on problem 2 didn't kill me. recruiter said they evaluate holistically.
this was for Samsung MX (mobile experience) division in Mountain View. i've heard the Samsung Research OA is slightly different in structure but similar difficulty range.
if you're in the leetcode medium range comfortably, you'll be fine. don't go in expecting hard-only problems but don't assume easy either.