The Day I Almost Blew My Interview

My hands were shaking. The interviewer asked a question I had no idea how to answer.

It was winter 2023. I was sitting in a Google interview room, facing a serious-looking engineer. He had just asked me an algorithm question:

"Given a binary tree, find the largest BST subtree."

My mind went completely blank.

I knew what a binary tree was. I knew what a BST (Binary Search Tree) was. But "largest BST subtree"? The phrase kept spinning in my head, but I couldn't piece together a complete solution.

My hands started shaking uncontrollably. I gripped the whiteboard marker, trying to calm myself down, but my heartbeat was so loud I could hear it myself.

"It's okay, take your time," the interviewer said. But in his tone, I detected a hint of... impatience? Or was I overthinking?

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The Disaster Begins

For the first five minutes, I stood in front of the whiteboard, writing nothing.

Countless thoughts flashed through my mind:

• "Should I traverse the entire tree first?"
• "Do I need recursion? Or iteration?"
• "What's the BST validation condition again? Left smaller, right larger, and then what?"
• "I'm screwed. I don't even fully understand the question..."

I tried to draw a tree on the whiteboard, but stopped halfway. Because I didn't know where to go next.

The interviewer watched me, saying nothing. That silence was more painful than any criticism.

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I Almost Gave Up

"Just give up. You don't know it anyway."

This thought grew louder and louder in my mind.

I started thinking:

• "This interview is already over"
• "I'm not fit for this company"
• "I should just say I don't know and end this torture"
• "I won't pass anyway, why waste time?"

I had even started forming the words in my head: "Sorry, I don't know this problem. Can we skip it?"

But just as I was about to speak, I remembered something I'd read before the interview:

"An interview is not an exam. An interview is a work simulation."

What does that mean?

It means: at work, you'll encounter problems you don't know how to solve. What will you do then? Give up immediately? Or find a way to solve it?

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But I Did One Thing

I took a deep breath.

Then, I said something that surprised even myself:

"I haven't encountered this problem before, but can I walk through my thought process?"

The interviewer nodded. "Of course."

I started talking:

"First, I understand that a BST is defined as: for each node, all values in the left subtree are smaller than it, and all values in the right subtree are larger. Then, the problem asks for the 'largest BST subtree' - I understand this as the subtree with the most nodes..."

I paused here. "But I'm a bit uncertain - does 'largest' mean most nodes, or maximum depth?"

The interviewer spoke up: "Most nodes."

He gave me a hint!

---

I Started Talking, Even Without the Answer

For the next ten minutes, I thought out loud:

"So my approach is: starting from the root, check if each subtree is a BST. If it is, record its node count. Finally, return the one with the most nodes..."

"But this doesn't seem very efficient, because it would involve repeated calculations..."

"Is there a way to check from the bottom up? First check leaf nodes, then go up..."

I talked while drawing on the whiteboard. Although my solution wasn't optimal, although I got stuck several times, I kept talking, kept thinking.

And the interviewer kept listening.

Several times, he said: "You can think about this part more." Or "If you do it this way, what problems might arise?"

He wasn't testing me. He was helping me.

---

The Interviewer's Response

Twenty minutes later, I had written a solution. Not the optimal one - time complexity was O(n²) - but it was correct.

The interviewer looked at the whiteboard and said:

"Your thought process was good. Actually, this problem has an O(n) solution. Think about it - can you optimize?"

He gave me another minute to think, then started explaining the optimization approach. I listened, nodded, and modified the code on the whiteboard.

Finally, he said:

"You didn't completely solve this problem, but your thought process and problem-solving ability are exactly what we need."

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The Unexpected Outcome

A week later, I received an offer.

I was shocked. I clearly hadn't solved that problem - why was I still hired?

Later, I had another conversation with that interviewer. He told me:

"At Google, we're not looking for people who memorize answers. We're looking for people who can stay calm, communicate proactively, and seek solutions when they encounter problems they don't know."

"What you did that day is exactly what we want to see: admitting you don't know, but not giving up; showing your thought process instead of staying silent; accepting hints and then improving."

"That's more important than solving one problem."

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What I Learned

That interview completely changed my understanding of what an "interview" is:

Advice for You: What to Do When You're Stuck

If you encounter a problem you don't know in an interview, try this:

Step 1: Admit You Don't Know, But Don't Give Up

Say: "I haven't seen this problem before, but I can try."

Step 2: State Your Understanding

Say: "Let me first explain how I understand the problem..." Then restate it to confirm you haven't misunderstood.

Step 3: Show Your Thought Process

Say: "My initial approach is..." Then start analyzing, even if it's an incomplete thought.

Step 4: Proactively Seek Help

Say: "I'm stuck at this point. Could you give me a hint?"

Step 5: Accept the Hint and Move Forward

After the interviewer gives a hint, say: "Thanks, let me try this direction..."

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Final Words

That day, I almost blew it. But precisely because I didn't give up, I had the chance to show my true self.

Interviews aren't about being perfect. They're about being authentic.

Authentic thinking. Authentic communication. Authentic problem-solving.

Next time you interview, if you encounter a problem you don't know, remember:

Not knowing is okay. Giving up is what's scary.

Speaking your thoughts is more powerful than silence.

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Remember: An interview is not an exam. It's a work simulation. Just be your authentic self.