Top 10 DSA Questions to Crack Your Next Coding Test

6. Implement a Stack Using Queues

This problem tests your understanding of data structures by implementing one data structure using another.

• Approach:
  Use two queues to mimic the behavior of a stack.
• Tips:
  Focus on the push and pop operations to maintain the Last-In-First-Out (LIFO) property.

Key Points:

• Time Complexity: Varies based on implementation.
• Space Complexity: O(n)

Bullet Points:

• Enhances understanding of abstract data types.
• Good exercise in adapting data structure operations.
• Often discussed in system design interviews.

7. Evaluate a Postfix Expression

Evaluating postfix expressions requires understanding of stacks and operator precedence.

• Approach:
  Use a stack to push operands and apply operators as they appear.
• Tips:
  Ensure correct handling of operator precedence and edge cases like division by zero.

Key Points:

• Time Complexity: O(n)
• Space Complexity: O(n)

Bullet Points:

• Simplifies the evaluation of complex expressions.
• Excellent for understanding stack-based algorithms.
• Frequently appears in coding assessments.

8. Find the Intersection of Two Arrays

This problem is useful to test your grasp of arrays and hash-based data structures.

• Approach:
  Use hash sets to store elements of one array and then check for common elements.
• Tips:
  Consider using sorting as an alternative approach if extra space is a concern.

Key Points:

• Time Complexity: O(n + m)
• Space Complexity: O(min(n, m))

Bullet Points:

• Good for learning hash-based algorithms.
• Demonstrates the importance of data structure choice.
• Common in online coding challenges.

9. Implement Queue Using Stacks

Creating a queue using two stacks is a common problem that demonstrates the versatility of stack operations.

• Approach:
  Use two stacks: one for enqueue operations and another for dequeue operations.
• Tips:
  Balance the operations to ensure efficient amortized performance.

Key Points:

• Time Complexity: O(n) worst-case for dequeue, amortized O(1)
• Space Complexity: O(n)

Bullet Points:

• Reinforces understanding of stack operations.
• Demonstrates data structure transformation.
• Practical for interviews focusing on problem-solving skills.

10. Solve the Two Sum Problem

The two sum problem is widely popular and tests both brute-force and optimized approaches using hash maps.

• Approach:
  Use a hash map to check for the complement of each element.
• Tips:
  Handle cases where there are multiple valid answers by clarifying the problem constraints.

Key Points:

• Time Complexity: O(n)
• Space Complexity: O(n)

Bullet Points:

• Foundation for understanding hash-based searches.
• Frequently asked in technical interviews.
• Enhances algorithm optimization skills.

Also Read: Top 10 DSA Questions on Linked Lists and Arrays

Effective Strategies to Solve DSA Problems

Developing a robust strategy for solving DSA problems can make a significant difference during coding tests. By breaking down problems into smaller, manageable parts, you can approach each problem with a clear mind and a step-by-step plan.

Plan Your Approach

Before diving into the code, spend some time planning:

• Understand the Problem:
  Read the question carefully and make sure you fully understand the requirements.
• Identify the Data Structures:
  Determine which data structures (arrays, linked lists, stacks, etc.) are most appropriate.
• Outline a Strategy:
  Draft a plan or pseudocode to structure your solution.

Practice Regularly

Consistency is key. Regular practice helps you to:

• Improve speed and accuracy:
  Regularly solving problems increases your familiarity with common patterns and techniques.
• Build intuition:
  Over time, you will recognize which approaches work best for different types of problems.
• Boost confidence:
  Frequent practice reduces anxiety during real coding tests.

Bullet Points for Effective Strategies:

• Break problems into smaller parts.
• Write pseudocode before coding.
• Test edge cases and validate your solution