Leetcode is a popular website for coding enthusiasts and software engineers who want to practice their problem-solving skills. It features a vast collection of algorithmic challenges, from easy to hard, that can help you improve your coding proficiency and prepare for technical interviews. However, solving Leetcode problems can be intimidating, especially if you are new to programming or have never encountered specific algorithms or data structures. This article will explore strategies and techniques to help you solve leetcode problems efficiently and effectively and answer the question “How To Solve Leetcode Problems.”

Understand the problem statement

The first stage of resolving any leetcode problem is carefully reading and understanding the problem statement. Ensure you have a clear knowledge of what the problem is asking you to accomplish, the inputs and outputs, and the constraints and requirements. Take notes if necessary, and try rephrasing the problem statement in your own words to ensure you have a solid grasp of the problem. Once you have understood the problem, you can move on to the next step.

Identify the problem type

The next step is to identify the type of problem you are dealing with. We can categorise Leetcode problems into an array, string, linked list, tree, graph, dynamic programming, etc. Each type of problem requires a different approach and set of techniques. For example, if you are dealing with an array problem, you may need to use loops and indexing to access and manipulate the elements of the array. If you are dealing with a tree problem, you may need recursion and traversal to traverse the tree nodes. Understanding the problem type can help you choose the proper data structure and algorithm to solve the problem efficiently.

Solve the problem manually

Before you start coding, it is a good idea to solve the problem manually using pen and paper. This can help you visualise the situation and devise a plan of action. Try to solve the problem step by step, and record each step you take. This will help you identify patterns or insights helpful in designing an algorithm. Additionally, manual solving can help you catch any edge cases or special conditions that may not be immediately apparent from the problem statement.

Let’s take an example to understand the problem manually:

Array: [2, 7, 11, 15]
Target: 9

1. Design an algorithm

Once you understand the problem and identify the problem type, you can start designing an algorithm. A step-by-step procedure for solving a problem is called an algorithm, and one can represent it using pseudocode or a flowchart. When designing an algorithm, you should consider the following:

  • Which data structure(s) will we use?
  • What is the time complexity of the algorithm?
  • What is the space complexity of the algorithm?
  • Which edge cases and special conditions require consideration?

When designing an algorithm, strive to break down the problem into smaller subproblems that individuals can solve independently. This can make the problem more manageable and easier to solve.

2. Code the algorithm

Once you have designed an algorithm, you can start coding it. Ensure you follow best practices, such as using meaningful variable names, commenting on your code, and writing test cases. When coding the algorithm, you should consider the following:

  1. Does the code compile?
  2. Does the code produce the expected output for the test cases?
  3. What is the time complexity of the leetcode?
  4. Do we need to handle any edge cases or special conditions?
  5. What is the space complexity of the leetcode?
  6. Test and debug the code


def two_sum(nums, target):
    num_to_index = {}  # Hash map to store numbers and their indices
    for index, num in enumerate(nums):
        complement = target - num
        if complement in num_to_index:
            return [num_to_index[complement], index]
        num_to_index[num] = index
    return None  # No valid solution found

# Test the function
nums = [2, 7, 11, 15]
target = 9
print(two_sum(nums, target))  # Output: [0, 1]

3. Test the code

After you have written the code, you should test it thoroughly to ensure it works as expected. You can use leetcode’s built-in and your test cases to validate the code. When trying the code, you should consider the following:

  • Does the code produce the expected output for all test cases?
  • Does the program fail to handle any edge cases or special conditions correctly?
  • Are there any logical errors or syntax errors in the code?
  • Is the code readable and maintainable?

If you encounter any issues during testing, you should debug the code by tracing the execution path and examining the values of variables and data structures. Use print statements or a debugger to help you identify the source of the problem. Once you have fixed the issue, retest the code to ensure it works correctly.

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4. Optimise the code

After you have tested and debugged the code, you can try to optimise it to make it more efficient. This can involve reducing the algorithm’s time or space complexity or improving the code’s readability and maintainability. When optimising the code, you should consider the following:

  • Can the algorithm be simplified or optimised?
  • Can the data structure be modified to reduce the time or space complexity?
  • Are there any redundant or unnecessary operations in the code?
  • Can the code be refactored to improve readability and maintainability?

However, optimising the code can sometimes lead to decreased readability and maintainability. Only optimise the code if you are confident it will not introduce new bugs or make it harder to understand.

I solved 541 Leetcode problems. But you need only 150.

5. Submit the solution

Once you have completed the problem, you can submit your solution on leetcode. Leetcode will test your solution against a set of test cases and provide feedback on whether your answer is correct and, if not, where the problem lies if your key passes all the test cases. Congratulations! You have solved the problem. If not, go back and review your code to find the source of the problem. Remember, the goal is not just to solve the problem but to solve it efficiently and correctly.

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Tips for solving leetcode problems

Here are some tips for solving LeetCode problems:

1. Start with easy problems

If you are new to LeetCode or algorithmic problem-solving, start with easy problems. LeetCode designed these problems to help you understand how to approach and solve them.

2. Read the problem statement carefully

Before you start solving a problem, read the problem statement carefully. Understand what the problem is asking for and what the constraints are.

3. Understand the problem

Try to understand the problem and its requirements by considering a few sample inputs and outputs. This will help you identify the type of problem, the input format, and the output format.

4. Identify the suitable algorithm

Identify the most efficient algorithm or data structure for solving the problem. Practice and familiarity with standard algorithms and data systems will help you identify them.

Continue reading How To Solve Leetcode Problems

5. Plan your approach

Plan how to solve the problem before you start coding. Write down the steps, and make sure you have a clear plan of attack.

6. Write pseudocode

Once you have a plan, write down the pseudocode. It is a way of writing out the steps you will take to solve the problem in plain language before you write actual code.

7. Write code and test it

Once you have the pseudocode, write the actual code, test it thoroughly, and ensure it passes all the test cases.

8. Optimise your solution

If you have a working solution, optimise it for time and space complexity. This can help improve your understanding of algorithms and data structures.

9. Review and refactor your code

Continuously review and refactor it, even if it passes all the test cases. This will help you improve your code quality, readability, and maintainability.

Continue reading How To Solve Leetcode Problems

10. Practice, practice, and practice

Finally, practice as much as possible. The more problems you solve, the better you will become at problem-solving. Try to solve different situations, and keep challenging yourself with more complex problems as you improve.

Take Away

In conclusion, Solving leetcode problems can be a challenging but rewarding experience. Following the steps outlined above, you can approach leetcode issues with a structured and systematic mindset to help you solve them efficiently and effectively. Remember to understand the problem, identify the problem type, solve the problem manually, design an algorithm, code the algorithm, test and debug the code, optimise the code, and submit the solution. You can become a proficient problem solver and achieve your coding goals with practice and perseverance.

Answers to FAQs about Leet Problems

1. What are Leet’s Problems?

Leet (short for “elite”) Problems are coding challenges or puzzles involving transforming standard text into a more complex or obscure form of writing using a combination of letters, numbers, and symbols. These challenges often require a deep understanding of programming concepts and various programming languages.

2. Where did Leet’s Problems originate?

Programmers believe Leet Problems originated in the early days of online gaming, where players would use “leet speak” to communicate with one another in a more cryptic or secretive manner. Over time, this practice evolved into a coding challenge, with programmers using Leet to encode messages and solve increasingly complex puzzles.

3. What are some common Leet transformations?

Some common Leet transformations include replacing letters with numbers or symbols that resemble them, such as “4” for “A” or “3” for “E”. Other transformations might involve replacing entire words or phrases with abbreviations or acronyms, such as “LOL” for “laugh out loud” or “BRB” for “be right back”.

4. What are programming languages commonly used in Leet Problems?

Any programming language can write Leet Problems, although some programmers commonly use specific languages. For instance, they might use Python or Perl for challenges that involve string manipulation or regular expressions. Conversely, they might register challenges that include algorithms or data structures in C++ or Java.

5. What skills do you need to solve Leet’s Problems?

To solve Leet Problems, you typically need a strong foundation in programming concepts and algorithms and the ability to think creatively and analytically. You should also be comfortable working with various programming languages and tools and understand how to debug and test your code.

6. How do you approach a Leet Problem?

When approaching a Leet Problem, it’s essential to start by carefully reading and understanding the problem statement and any given constraints or requirements. From there, you can develop a plan or algorithm for solving the problem, which may involve breaking it down into smaller sub-problems or using a known data structure or algorithm. Finally, you must implement and test your solution, carefully considering edge cases and error handling.

7. What are some tips for solving Leet’s Problems?

Some tips for solving Leet Problems include regularly practising to build your skills and knowledge, breaking the problem into smaller, more manageable sub-problems, and being comfortable with trial and error. It would be perfect if you also were willing to ask for help from peers or online resources and be persistent in solving the problem.

8. How can Leet Problems help with programming skills?

Solving Leet Problems can help improve your programming skills in several ways. For example, it can help to build your knowledge of algorithms and data structures, improve your problem-solving skills, and teach you how to think creatively and analytically. It can also help you to become more comfortable with various programming languages and tools and give you a deeper understanding of how they work.

9. Where can you find Leet’s Problems to solve?

You can find Leet Problems on various online platforms and websites, including LeetCode, HackerRank, Codeforces, and more. Many of these sites offer a wide range of challenges, from easy to complex, and forums and communities where you can connect with other programmers and get help with solving problems.

10. How can you get started with solving Leet’s Problems?

To get started with solving Leet Problems, you can begin by practising with simple challenges and working your way up to more complex problems over time. You can also enroll in online trainings, courses or tutorials to build your programming skills and learn new algorithms and techniques. Many online resources, such as LeetCode and HackerRank, offer free or low-cost access to Leet Problems and forums and communities where you can connect with other programmers and get help with solving problems. Additionally, you can try participating in coding competitions or challenges, which can help you to develop your skills and challenge yourself to improve. With consistent practice and persistence, you can become proficient in solving Leet Problems and strengthen your programming abilities.

J. Shaw

Joseph Shaw is a renowned expert with two decades of experience in health and fitness, food, technology, travel, and tourism in the UK. His multifaceted expertise and commitment to excellence have made him a highly respected professional in each field.

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