> Right now, I am struggling with all the interviews that have these leetcode problems.

There's no need to struggle with them. You'll cover fully half of them simply with experience with trees. Build them. Traverse them top-down. Then bottom-up. Search it, Balance it, then rebalance on modification. Invert it, prune it, Roundtrip it to JSON, etc.

After mastering that, given a problem of "develop a flood-fill algorithm to this specification" should be a walk in the park.

Off the top of my head, possible problems here might be:

1. To handle trees easily you have to understand recursion. Somebody with no CS experience (and no parser experience) might never ever used recursion in anger, even if they launched zillion commercial projects.

2. No Big-O notation. Interviewers usually ask questions about time/space complexity.

And the elephant in the room is that leetcodes are getting trickier and trickier, that's LLM era for you.