How to Approach a Competitive Programming Question | FACE Prep

How to Approach a Competitive Programming Question | FACE Prep

How to Approach a Competitive Programming Question

Are you preparing for competitive coding contests? Whether you’re just getting started or you’re already in the thick of it, mastering the process of approaching problems efficiently is key to success. In this article, we will walk you through a proven step-by-step method to help you tackle competitive coding challenges effectively. Follow this guide, and you’ll not only boost your problem-solving skills but also improve your speed and accuracy.

How to Get Started with Competitive Coding

Before we dive into the steps, make sure to check out some of the popular websites where you can practice competitive coding problems, such as:
  • Codeforces
  • LeetCode
  • HackerRank
  • CodeChef
  • TopCoder
These platforms offer a variety of challenges, ranging from beginner to expert level.

Step-by-Step Approach to Solving Competitive Coding Problems

Let’s break down the problem-solving process. Here’s a structured approach that will help you understand how to analyze and solve any coding problem effectively:

1. Understand the Problem Statement

The first step in competitive coding is to fully understand the problem. Read the problem statement carefully and several times if needed. Try to relate the problem to real-life scenarios or visualizations to make it easier to grasp. Let’s take a look at an example:Problem Statement: You own a departmental store and are given the stock prices for seven days. Your task is to determine the best days to buy and sell stocks to make the maximum profit.Sample Input:
100, 180, 260, 310, 40, 535, 695
Sample Output:
csharp
Buy stock on day 1 (100) Sell stock on day 4 (310) Buy stock on day 5 (40) Sell stock on day 7 (695)

2. Analyze the Problem

Next, analyze the problem in more detail. Ask yourself the following questions:
  • Can I explain the problem to a layman?
  • What inputs are required, and what should the output look like?
  • Can I break down the problem into smaller, manageable chunks?
For our stock price problem:
  • Input: A list of stock prices for each day.
  • Output: The specific days when to buy and sell stocks to maximize profit.

3. Understand Input/Output (I/O)

Understanding the input format and expected output is crucial. This step helps you identify edge cases and constraints. Let’s go over the sample inputs and outputs.For the problem above, the input will consist of stock prices for seven days, and you will output the days to buy and sell along with the prices.Example:
  • Test Case 1: Input: [50, 100, 120, 130, 250]
    • Output: Buy stock on day 1 (50), Sell stock on day 5 (250)
  • Test Case 2: Input: [140, 20, 150, 10, 350]
    • Output: Buy stock on day 2 (20), Sell stock on day 3 (150), etc.

4. Break Down the Problem into Smaller Tasks

When a problem seems large, break it down into smaller sub-problems. For this stock price problem:
  1. Find the minimum price: Determine the best day to buy.
  2. Find the maximum price: Determine the best day to sell after the buying day.
  3. Repeat until all days are processed.
By breaking down the problem, you will simplify the implementation.

5. Write the Code

Now it’s time to implement the solution. Start writing the code by focusing on solving one sub-problem at a time. Here’s how the code might look for our problem:
python
list = [100, 180, 260, 310, 40, 535, 695]# Finding minimum stock price def findMin(list): for i, val in enumerate(list[:-1]): if val < list[i + 1]: return i, val return –1, –1# Finding maximum stock price def findMax(list): for i, val in enumerate(list[:-1]): if val > list[i + 1]: return i, val return i + 1, list[-1]def buySellStock(): index = 0 while index < len(list): i, val = findMin(list[index:]) if i > –1: index = i + index print(“Buy stock on day “, index + 1, “(“, val, “)”, sep=”) else: breaki, val = findMax(list[index:]) index = i + index print(“Sell stock on day “, index + 1, “(“, val, “)”, sep=”)buySellStock()

6. Test and Optimize the Solution

Once you’ve written the code, it’s essential to test it with various test cases. Here are some example test cases:
  • Test Case 1: [50, 100, 120, 130, 250] → Output: Buy stock on day 1 (50), Sell stock on day 5 (250)
  • Test Case 2: [140, 20, 150, 10, 350] → Output: Buy stock on day 2 (20), Sell stock on day 3 (150), etc.
Check whether your solution passes all test cases. If it does, great! If not, debug and make improvements. You can also optimize the code by reducing the time complexity.

Important Considerations in Competitive Programming

While solving problems, keep these key points in mind:

1. Compile Time Errors:

These errors occur due to incorrect syntax. Be careful as many platforms have a limited number of compile attempts.

2. Run Time Exceptions:

Common runtime issues include dividing by zero, accessing out-of-bound memory, or using excessive array sizes. Always be mindful of these.

3. Time Complexity:

Ensure your solution meets the problem’s time constraints. If the time limit is 1 second, avoid solutions with higher time complexity, like O(n^2).

4. Memory Constraints:

Make sure your solution is memory-efficient. Using large arrays or unnecessary data structures can result in memory-related errors.

Conclusion

By following this structured approach to competitive programming, you will be better prepared to tackle problems efficiently and effectively. With practice, you will sharpen your skills and be able to solve problems quickly, even under time pressure.