Interview-English-Phrasebook

這篇在解決什麼

這不是英文教材。這裡只收**「讀得懂、但當場講不出來」**的那些——你看到 l = m + 1 完全知道它在幹嘛，但要用嘴巴講給面試官聽的那三秒鐘，腦袋是空的。

收錄標準有兩條：

1. 唸不出來的：符號、發音陷阱、把一整段 code 講成人話。
2. 知道這個字就省一整句的：不知道 in-place，你得說「不用額外的陣列，直接改原本那個」；知道了就是兩個字。

一、符號怎麼唸

二、真的會唸錯的字

三、知道這個字，就省一整句

這節是本篇的重點：左邊是你想表達的東西，右邊是那個字，最右邊是不知道它的時候你會怎麼卡。

樹

圖

四、把一整段 code 講成人話

反例與正解對照。同一段二分搜尋：

int l = 0, r = nums.size() - 1;
while (l <= r) {
  int m = l + (r - l) / 2;
  if (nums[m] == target) return m;
  if (nums[m] < target) l = m + 1;
  else r = m - 1;
}
return -1;

✗ 逐字唸（面試官聽不出你懂不懂）

"int el equals zero, int ar equals nums dot size minus one. While el less than or equal ar, int em equals el plus r minus l over two. If nums of em equals target, return em..."

✓ 講意圖（同樣長度，資訊量完全不同）

"I keep a closed interval [left, right] that always contains the answer if it exists. Each round I look at the midpoint — I write it as left + (right - left) / 2 to avoid overflow rather than (left + right) / 2. If it's the target I'm done. If it's too small, the answer must be strictly to the right, so I move left past mid; otherwise I move right below mid. If the interval becomes empty, the target isn't there, so I return minus one."

差別在三處，每一處都是面試官在打分的地方：

1. 說出不變量（"always contains the answer"），不只說步驟。
2. 說出為什麼這樣寫（"to avoid overflow"），這是主動送分。
3. 說出為什麼可以丟掉一半（"must be strictly to the right"），證明你不是背模板。

模板本身見 Binary-Search-Templates。

五、面試流程句型

開場釐清（問了不扣分，不問才扣）

• "Let me make sure I understand the problem — you want ..., right?"
• "How large can n get?" ← 這句直接告訴你該做 O(n log n) 還是 O(n)
• "Can I assume the input is non-empty / sorted / fits in a 32-bit integer?"
• "Are there duplicates?" ／ "Can the values be negative?"
• "What should I return for an empty input?"
• "Is it okay if I modify the input in place?"

提出思路（先講再寫，永遠）

• "Let me walk you through my approach before I write any code."
• "The brute-force would be to check every pair — that's O(n²). Let me see if I can do better."
• "The key observation is that ..."
• "I'll trade space for time here — a hash map makes the lookup O(1)."
• "Let me start with something correct and optimize afterwards."
• "This reduces to a problem I've seen before — it's basically ..."

邊寫邊講

• "I'll pull this out into a helper so the main function stays readable."
• "I'm handling the empty case up front so the loop below doesn't need to worry about it."
• "I'll call this seen — it holds the values we've already visited."
• "This is the part I mentioned earlier where ..."

講複雜度（主動講，別等人問）

• "This runs in O(n log n) time, dominated by the sort."
• "Space is O(h), where h is the height — O(log n) if the tree is balanced, O(n) in the worst case when it degenerates into a chain."
• "The amortized cost per operation is O(1), even though a single resize is O(n)."
• "O(n) is optimal here — you have to look at every element at least once."

手動跑一次

• "Let me trace through an example to make sure this is right."
• "Say the input is [1, 2, 3]. First iteration, i is zero, so ..."
• "Let me check the edge cases: empty input, a single element, all negatives."

卡住的時候（重點：不要安靜）

• "Let me take a step back." ← 萬用，爭取時間又聽起來有控制感
• "I'm not seeing the optimal solution yet — let me think out loud for a second."
• "I have an O(n²) approach. I suspect there's a linear one using a hash map — does that sound like the right direction?"
• "Am I on the right track?" ／ "Could you give me a nudge?"
• 「我不知道」不要講成 "I don't know"，講成："I'm not sure yet, but here's what I do know: ..."

發現自己寫錯

• "Actually, hold on — that breaks if the array has duplicates."
• "Good catch. Let me fix that."
• "I need to move this line above the loop."
• 不要道歉超過一次。"Let me fix that" 就夠了，sorry 說三次只會顯得慌。

討論取捨與收尾

• "There's a trade-off: the hash map gives O(1) lookup but costs O(n) extra space. If memory were tight I'd use the two-pointer version."
• "It's faster in practice, but asymptotically the same."
• "I think that's it. Want me to go through the complexity again, or try another test case?"

六、中式英文陷阱

Related Problems

• Binary-Search-Templates — 第四節那段示範 code 的完整模板與推導
• Tree-Traversal-Iterative — preorder／inorder／postorder 這幾個字對應的實作
• 0124-Binary-Tree-Maximum-Path-Sum — downward path／LCA 這組術語的出處
• STL-Pitfalls — 面試被追問「為什麼不用這個容器」時的彈藥