got OA in November via hackerrank, really hard DP problems. cannot solve any problems and was rejected several days later. The problems were even very hard to understand, didn't have a great experience, seem they only want geniuses who won competitions.

After OA, I had a LLD round where I had to use best OOPs design principles and design patterns to basically provide a running code with test cases. The question was in multiple parts and the difficulty increases at each level.