Finally I got a chance to write out a post for LC community to extend my appreciation. Learned so much from here and I will continue to be a loyal premium member of it :)

So first some brief introduction about my background and LC status:

• PhD in Bio-related field from top10 U.S. university. Lots of coding experience in my current company as a Reseacher (YOE is ~2yr, but I'm not sure if this all counts as I'm not a SWE in my current position).
• LeetCode status: ~1000 problems solved in ~1 year of timeframe. 180 easy, 560 medium and 250 hard. Google past 6-month questions (~350 questions) finished twice. Weekend contest 95% time can solve 3 problems in 40min - 1hr. 50% time get Q4 done.

Google timeframe:

• Referred by a friend at around mid June. Contacted by HR late June. Directly skipped the phone interview. Asked ~1 month for virtual onsite prep
• VO at early Aug. HR took ~3 weeks to get feedback, sent to HC (target L4). HC asked for two more rounds of coding
• Extra two rounds finished one week ago. Get approval this week, and gave L3.

Due to NDA, cannot disclose the exact question. But I will try to provide similar question you can find on LC.

• Round 1 (Hard): DFS type string construction question. Follow-up: Trie-based question. Similar question: 527. Word Abbreviation

• Round 2 (Medium with 6 follow-ups): DFS type tree-related question as well as tree validation. Similar question: 1376. Time Needed to Inform All Employees

• Round 3 (Medium to hard): Union find type question. Similar question: 399. Evaluate Division

• Round 4 (Hard): Tree iterator. Similator question: cannot find.

• Extra Round 1 (Real Hard): String type question. This is an exact LC hard level question (sorry I cannot point it out). But the interviewer knew this and banned all the approaches provided in the Solution and discussions I can find. But thank god, I found the approach he wanted.

• Extra Round 2 (Hard): DP type question. Similar problem: 975. Odd Even Jump (this is the closest I can find, but still are somewhat different)

Some tips and takeaways:

• CLARIFY the question before even start to think about possible approaches. Google really like to give you ambigous questions and need you to figure out what they want.
• To sure to speak out your thoughts and get agreemetns on the approach you are going to take before writing down formal codes.
• Demonstrate your thought process is more important than a bug-free code. Actually, several rounds I didn't provide a bug-free code in the first attempt. Interviewers raised some questions to help me identy those.
• PRACTICE! I know my LC status might be on the high end with 1k problems solved. But to me, the more problems I saw, the easier I can connect the dots and see the pattern behind. For the Real Hard round I mentioned, my idea came from a completely different type question that I practiced on LC. For someone who is not born to be coding genius, this is what I can do to maximize my chance.
• Currently I have to say is a especially difficult period for job hunting. The bar for these large companies are much higher. But please trust yourself. As long as you are walking towards your dream and fight for it. You can get it eventually!

P.S. Heard team match is a painful process nowadays in Google. Wish myself luck!

Update: received offer today - took ~1.5 weeks for team match. Way faster than I expected.