_Template-Problem

[Problem Title] — LeetCode #[Number]

Metadata

Difficulty: Easy / Medium / Hard Date: YYYY-MM-DD Topic Tags: Array, Hash Map, Two Pointers, … Source: Roadmap-FAANG → Buổi XX

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1. Problem Statement

Paste problem statement here hoặc link: LeetCode XXX

Input: Output: Constraints:

• $1\le n\le 10^5$
• $-10^4\le \text{nums}[i]\le 10^4$

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2. Clarification Questions (Ask in interview!)

Trước khi code, hỏi interviewer

• Input có thể empty không? Edge case với n = 0?
• Có negative numbers không?
• Có duplicates không? Ảnh hưởng gì?
• Return gì nếu không có answer?
• Cần in-place hay được tạo array mới?

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3. Pattern Recognition

Map problem → pattern

Signal words: ”…” → Pattern: [Two Pointers / Sliding Window / DP / …]

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4. Approaches

Approach 1: Brute Force

• Idea: …
• Time: $O(N^2)$ | Space: $O(1)$
• Why not: Timeout với $N=10^5$

Approach 2: Optimal — [Pattern Name]

• Idea: …
• Time: $O(N\log N)$ | Space: $O(N)$
• Why this works: …

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5. Implementation

/**
 * [Problem Name] — LeetCode #XXX
 *
 * Approach: [Brief description]
 * Time: O(...) | Space: O(...)
 */
function solveProblem(/* params */): /* return type */ {
  // Edge cases
  if (/* condition */) return /* base case */;
 
  // Main logic
 
 
}
 
// Test cases
console.assert(solveProblem(/* input */) === /* expected */);
console.assert(solveProblem(/* edge case */) === /* expected */);

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6. Complexity Analysis

	Time	Space
Brute force	$O(N^2)$	$O(1)$
Optimal	$O(N)$	$O(N)$

Bottleneck: [Which step dominates?]

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7. Edge Cases Tested

• Empty input
• Single element
• All same elements
• Already sorted / reverse sorted
• Negative numbers
• Integer overflow scenario

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8. What I Learned

Key Takeaway

[Insight mới, pattern mới, hoặc mistake đã học được]

Mistake made: … Correct approach: … Next time I see ”…” in the problem, I will think of …

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9. Similar Problems

• — Same pattern
• — Variant with extra constraint

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Added: YYYY-MM-DD | Reviewed: — | Confidence: ⭐⭐⭐