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Coding Challenges

Welcome to the COLY Challenges section! Here you'll find coding exercises, katas, and problems to test and improve your programming skills.

What are Coding Challenges?​

Coding challenges are small, focused problems designed to help you:

  • Practice what you've learnt in the courses
  • Strengthen your problem-solving skills
  • Build confidence in writing code
  • Prepare for technical interviews
  • Have fun whilst learning!

How to Use These Challenges​

1. Choose Your Level​

Start with challenges that match your current skill level:

  • Beginner: Basic syntax, variables, loops, and conditions
  • Intermediate: Functions, arrays, and more complex logic
  • Advanced: Algorithms, data structures, and optimisation

2. Try It Yourself First​

Before looking at the solution:

  1. Read the problem carefully
  2. Think about the approach
  3. Write your code
  4. Test with the provided examples
  5. Debug any issues

3. Learn from Solutions​

After attempting the challenge:

  • Compare your solution with the provided one
  • Understand different approaches
  • Learn better coding practices
  • Optimise your solution

Challenge Categories​

Beginner Challenges​

  • Basic calculations and string manipulation
  • Simple loops and conditions
  • Input validation
  • Pattern printing

Intermediate Challenges​

  • Working with arrays
  • String algorithms
  • Number theory problems
  • Searching and sorting

Advanced Challenges​

  • Complex algorithms
  • Data structures
  • Performance optimisation
  • Real-world problem solving

Tips for Success​

Before You Start​

  1. Understand the Problem: Read it multiple times if needed
  2. Plan Your Approach: Think before you code
  3. Consider Edge Cases: What could go wrong?
  4. Start Simple: Get something working first

Whilst Coding​

  1. Use Meaningful Names: Make your code readable
  2. Test Frequently: Don't wait until the end
  3. Break It Down: Split complex problems into smaller parts
  4. Comment When Needed: Explain tricky parts

After Solving​

  1. Review Your Code: Can it be improved?
  2. Test Edge Cases: Try unusual inputs
  3. Optimise: Can you make it faster or cleaner?
  4. Learn: What did this challenge teach you?

Testing Your Solutions​

Create a Test File​

public class ChallengeTest {
    public static void main(String[] args) {
        // Test case 1
        int result1 = yourFunction(input1);
        System.out.println("Test 1: " + (result1 == expected1 ? "PASS" : "FAIL"));

        // Test case 2
        int result2 = yourFunction(input2);
        System.out.println("Test 2: " + (result2 == expected2 ? "PASS" : "FAIL"));

        // Add more test cases...
    }
}

Test Different Scenarios​

  • Normal cases: Typical expected inputs
  • Edge cases: Minimum, maximum, boundary values
  • Invalid inputs: Negative numbers, empty strings, null values
  • Special cases: Zero, one, very large numbers

Common Mistakes to Avoid​

1. Not Reading Carefully​

// Problem: Return the sum of all EVEN numbers from 1 to n
// Wrong - includes odd numbers
for (int i = 1; i <= n; i++) {
    sum += i;
}

// Correct
for (int i = 2; i <= n; i += 2) {
    sum += i;
}

2. Off-by-One Errors​

// Wrong - misses last element
for (int i = 0; i < array.length - 1; i++) {
    // ...
}

// Correct
for (int i = 0; i < array.length; i++) {
    // ...
}

3. Not Considering Edge Cases​

// What if the array is empty?
// What if the number is negative?
// What if the string is null?

// Always validate inputs!
if (array == null || array.length == 0) {
    return 0;  // or throw an exception
}

Getting Stuck?​

If you're struggling with a challenge:

  1. Break It Down: Solve smaller parts first
  2. Use Examples: Work through the examples manually
  3. Draw It Out: Visualise the problem
  4. Google Similar Problems: Learn patterns (but don't copy solutions!)
  5. Ask for Help: Discuss with others, but understand the solution

Practice Makes Perfect​

The key to becoming a better programmer is consistent practice. Try to:

  • Solve at least one challenge per day
  • Revisit old challenges and improve your solutions
  • Challenge yourself with harder problems
  • Explain your solutions to others

Ready to Start?​

Browse the challenges below and pick one that interests you. Remember, it's not about getting it right immediately—it's about learning and improving with each attempt.

Good luck, and happy coding! 🚀

External Resources​

Want more practice? Check out these platforms: