Array Practice Problems
Building Muscle Memory
Reading about arrays is one thing; manipulating them fluently is another. These practice problems are designed to reinforce the concepts from the previous pages and build the intuition you'll need for more complex algorithms.
Each problem includes:
- A clear problem statement with examples
- Hints that guide you toward the solution without giving it away
- Edge cases to consider
- A complete solution with explanation
Work through them in order if you're new to arrays. Each problem builds on patterns from the previous ones.
Problem List
| Problem | Difficulty | Key Concepts |
|---|---|---|
| Find Maximum | Easy | Iteration, tracking state |
| Reverse Array | Easy | Two pointers, in-place swapping |
| Remove Element | Easy | In-place modification, shifting |
| Move Zeroes | Easy | Two pointers, relative order |
| Merge Sorted Arrays | Medium | Two pointers, merging |
| Rotate Array | Medium | Multiple approaches, tradeoffs |
Difficulty Guide
Easy problems focus on a single concept. If you understand the pattern, the implementation is straightforward.
Medium problems either combine multiple concepts or have subtle edge cases that require careful thought. They may also have multiple valid solutions with different tradeoffs.
How to Approach Each Problem
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Read the problem carefully. Make sure you understand what's being asked before writing code.
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Work through examples by hand. Trace through the given examples with pencil and paper. This often reveals the pattern.
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Consider edge cases. What happens with an empty array? A single element? All identical elements?
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Think before coding. Spend a few minutes planning your approach. What data do you need to track? How will you iterate?
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Start simple. Get a working solution first, even if it's not optimal. You can optimize later.
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Test your solution. Run through the examples mentally. Did you handle the edge cases?
Patterns You'll Practice
These problems introduce patterns that appear throughout algorithm problems:
- Tracking a running value (Find Maximum) - Keep track of the "best so far" as you iterate
- Two pointers (Reverse, Move Zeroes) - Use two indices that move toward each other or in the same direction
- In-place modification (Remove Element, Reverse) - Modify the array without allocating extra space
- Merging sorted data (Merge Sorted Arrays) - Combine two sorted sequences efficiently
- Multiple approaches (Rotate Array) - Recognize when problems have several valid solutions with different tradeoffs
Master these patterns here, and you'll recognize them in more complex problems later.