How long does it take to finish a LeetCode?

The time it takes to finish a LeetCode problem depends on several factors, such as your experience level, the difficulty of the problem, and your familiarity with the concepts involved. Let’s break down the factors and typical time estimates for solving different levels of problems on LeetCode.

1. Difficulty Level of the Problem

Easy Problems:

• Time Estimate: 15 to 30 minutes
• Why: These problems typically involve basic algorithms and data structures such as arrays, strings, and simple loops. If you have a good grasp of programming fundamentals, you can usually solve these problems quickly.
• Example: Problems like "Two Sum" or "Reverse Linked List" are relatively straightforward and require basic implementations.

Medium Problems:

• Time Estimate: 30 minutes to 1 hour (or more)
• Why: Medium problems often require more complex algorithms or a deeper understanding of data structures such as trees, graphs, or dynamic programming. They also require optimized solutions for larger inputs.
• Example: Problems like "Longest Substring Without Repeating Characters" or "Merge Intervals" may require you to think through various edge cases and use more advanced techniques.

Hard Problems:

• Time Estimate: 1 to 2 hours (or longer)
• Why: Hard problems are more challenging and require the application of advanced algorithms, dynamic programming, complex data structures like tries or segment trees, or optimization techniques.
• Example: Problems like "Word Ladder" or "Regular Expression Matching" often take longer because they require both time-efficient algorithms and deep problem-solving skills.

2. Experience Level of the Programmer

Beginner:

• Time Estimate:
  • Easy: 30 minutes to 1 hour
  • Medium: 1 to 2 hours
  • Hard: 2 hours or more
• Why: Beginners typically need more time to fully understand the problem statement, research algorithms, and debug their code. They may also have to look up syntax and language-specific details.

Intermediate:

• Time Estimate:
  • Easy: 15 to 30 minutes
  • Medium: 30 minutes to 1 hour
  • Hard: 1 to 2 hours
• Why: Intermediate programmers are comfortable with basic and some advanced algorithms. They can solve many problems more quickly but may still face challenges with more complex problems.

Advanced:

• Time Estimate:
  • Easy: 10 to 15 minutes
  • Medium: 20 to 45 minutes
  • Hard: 45 minutes to 1.5 hours
• Why: Advanced programmers are proficient in a wide range of algorithms and data structures, allowing them to solve even complex problems more efficiently. They are also adept at optimizing code and identifying the best approach quickly.

3. Factors Affecting the Time Taken

• Understanding the Problem: Some problems have tricky or complex problem statements that require extra time to fully comprehend. Ensuring you understand the input, output, and constraints can save time later on.
• Algorithm Choice: Choosing the right algorithm can make a big difference. If you start with a brute-force solution and then need to optimize, it may take longer to reach the final answer.
• Debugging: Some problems may introduce subtle edge cases that are not immediately apparent, leading to additional time spent on debugging and testing your solution.
• Optimization: Hard problems often require you to think about time and space optimization, which can add time if you're revisiting your initial approach to improve performance.

4. Tips for Solving LeetCode Problems More Efficiently

1. Break Down the Problem: Spend the first few minutes thoroughly understanding the problem. Break it down into smaller steps before jumping into coding.
2. Plan Before You Code: Write down your approach or pseudocode before starting the actual implementation. This can help prevent unnecessary rewrites.
3. Start with a Brute-Force Solution: If the optimal solution isn’t immediately apparent, try implementing a brute-force approach first. Once you have a working solution, focus on optimizing it.
4. Look for Patterns: As you practice, try to recognize common patterns (e.g., sliding window, two-pointer techniques, or dynamic programming) that can help you solve problems faster.
5. Review Solutions: After solving a problem, review other users’ solutions or the official solution to understand alternative approaches or optimizations.

5. Conclusion

The time it takes to finish a LeetCode problem varies based on the problem difficulty, your experience level, and the specific problem-solving approach. In general:

• Easy problems take around 15 to 30 minutes.
• Medium problems take 30 minutes to 1 hour.
• Hard problems can take 1 to 2 hours or more.

While experienced programmers can solve problems more quickly, beginners might need extra time as they develop their skills. Regardless of your experience level, practice, consistency, and learning from each problem are key to improving your speed and efficiency on LeetCode.