Algorithm questions are often challenging and intimidating, especially when you encounter unfamiliar ones in an interview or a test. How can you approach them with confidence and logic, without getting stuck or frustrated? In this article, we will share some tips and strategies that can help you tackle any algorithm question, even if you have never seen it before.
The first step is to understand the problem clearly and completely. Ask questions, clarify assumptions, define inputs and outputs, and restate the problem in your own words. Don't jump into coding or solving right away, as you might miss some important details or constraints. Try to identify the main goal, the edge cases, and the expected performance of the solution.
I once had a great interview at Google with a really vague problem statement. After a few questions, I knew the interviewer really expected me to dive deep on the problem before even thinking about a solution. After all, isn't it what we must do in a real job? More generally, in a coding interview context, you are often expected to ask questions to really understand what it is about. This is a nice way to assess your communication skills, so all you have to do is take a step back and ask genuine questions, such as: - Can I get some examples of inputs and outputs? - Are there some constraints in time or memory? - I see those edge cases, do you think I may have missed others? It's a discussion, so don't be afraid to talk.
The next step is to choose a method or a technique that can help you solve the problem. There are many methods that can be useful for algorithm questions, such as brute force, recursion, dynamic programming, divide and conquer, greedy, backtracking, and more. Depending on the problem, you might need to combine or modify some methods to fit the requirements. You can also use some common patterns or tricks that you have learned from previous questions, such as sorting, hashing, sliding window, binary search, and more.
In computer science, it is not usual to have more than one solution for a given problem. But more often than not, some solutions are better than others. In an interview context, choosing a method is about having a conversation with the interviewer. You may have several solutions in mind: in which case you have to explain them as well as their pros and cons (e.g. a better time complexity but a more complex implementation) and then choose with the interviewer what to implement. If you have only one solution in mind (or even only a partial solution), explain it to the interviewer: they may challenge you and give hints for some optimizations. You can ask questions, the interviewer is here to help you succeed as long as you are open minded.
The third step is to write pseudocode or a high-level outline of your solution. Pseudocode is a way of expressing your logic and steps in plain English, without worrying about syntax or implementation details. Writing pseudocode can help you organize your thoughts, check your logic, and communicate your solution to others. It can also make it easier to translate your solution into code later.
The fourth step is to code the solution based on your pseudocode or outline. Choose a programming language that you are comfortable with and that suits the problem. Follow the coding standards and conventions of the language and use meaningful names for your variables and functions. Avoid unnecessary complexity and redundancy and comment your code where needed. Test your code with some sample inputs and outputs and debug any errors or bugs.
The fifth step is to optimize the solution if possible or necessary. Optimization can involve improving the time or space complexity, reducing the number of operations, using better data structures, or simplifying the code. You can use some tools or techniques to analyze and measure the efficiency of your solution, such as Big O notation, time and space complexity, benchmarks, and profilers.
The final step is to explain the solution to others, such as the interviewer, the grader, or the reader. Explain your solution in a clear and concise way, using examples, diagrams, or analogies if needed. Highlight the main idea, the method, the trade-offs, and the advantages and disadvantages of your solution. Answer any questions or feedback that you might receive and show your understanding and reasoning skills.