Landing a software engineer role can feel like trying to hack into a mainframe with no access key—daunting, to say the least. You’ve fine-tuned your resume, networked like a Silicon Valley socialite, and now, the final boss awaits: the technical interview. But here’s a plot twist—most candidates approach coding interviews all wrong. Memorizing solutions? That’s rookie-level stuff.
Instead, let’s talk strategy. These 15 coding questions aren’t just a checklist; they’re your secret weapons for standing out. Let’s break them down, demystify them, and, most importantly, help you think like an engineer—not a code-regurgitating robot.
Why interviews aren’t just about syntax
Coding interviews aren’t a glorified LeetCode grind. They’re about problem-solving, communication, and demonstrating that you think like a software engineer. A HackerRank survey revealed that 90% of hiring managers value problem-solving skills above all else. So, if your plan is to cram and pray, you might want to rethink that strategy.
#15 Coding questions that interviewers love (and why they matter)
Here’s the list of must-know coding questions, categorized by topic. We’ll explain why each question matters and how to approach it.
1. Two sum
This is the classic warm-up question. It tests your ability to use hash maps for efficient lookups. Start with a brute-force solution, then optimize using a hash map to store complements. For example:
“Given an array of integers, return indices of the two numbers that add up to a specific target.”
2. Reverse a linked list
This question tests your understanding of pointers, a fundamental concept in linked lists. You can solve it using an iterative or recursive approach, each with its own trade-offs.
3. Merge two sorted arrays
This problem evaluates your ability to handle arrays efficiently. A common approach is using the two-pointer technique to merge the arrays in linear time.
4. Validate a binary search tree (BST)
A favorite in coding interviews, this question assesses your understanding of tree traversals. The best way to approach it is through in-order traversal to ensure the BST properties are maintained.
5. Longest substring without repeating characters
This question tests your ability to work with strings and sliding window techniques. A common solution is using a sliding window with a hash set to track unique characters.
6. Find the missing number
A test of mathematical reasoning and bit manipulation, this problem can be solved efficiently using the sum formula or XOR operation.
7. Implement a queue using stacks
A classic problem that challenges your understanding of stacks and queues. The best approach is using two stacks to simulate the queue’s FIFO behavior.
8. Detect a cycle in a linked list
This question evaluates your ability to detect cycles using Floyd’s Tortoise and Hare algorithm. The key technique involves two pointers moving at different speeds.
9. Maximum subarray (Kadane’s algorithm)
A common dynamic programming question that tests your optimization skills. Kadane’s algorithm helps find the maximum sum subarray in linear time.
10. Rotate an array
This problem challenges your ability to manipulate arrays efficiently. You can use reverse operations to rotate the array in place.
11. Lowest common ancestor in a binary tree
This question tests your understanding of tree traversal and recursion. The best approach is a recursive method to find the LCA of two nodes.
12. Design a LRU cache
A crucial system design question that evaluates your ability to use hash maps and doubly linked lists. The optimal approach combines both data structures to achieve O(1) time complexity for get and put operations.
13. Serialize and deserialize a binary tree
A fundamental problem in tree traversal and string manipulation. A common method involves using pre-order traversal to serialize and deserialize the tree.
14. Find the median of two sorted arrays
This question challenges you to optimize for logarithmic time complexity. A binary search-based partitioning approach is the best solution.
15. Word break problem
A test of dynamic programming and string operations. Using a DP array helps track whether substrings can be segmented into words.
Level up from candidate to standout engineer
Mastering these questions is just the start. Here’s how to truly level up:
✅ Understand the “why”—not just the “how.” Algorithms aren’t magic; they’re logic.
✅ Practice coding by hand. Whiteboards and notebooks still exist for a reason.
✅ Simulate real interviews. Practicing under timed conditions will help you build confidence and improve performance.
✅ Refine your problem-solving approach. Focus on breaking problems into smaller parts and tackling them methodically.
✅ Stay consistent. Set aside time each day to practice—small, consistent effort beats last-minute cramming.
Coding interviews don’t have to be intimidating. With the right preparation and mindset, you can tackle even the toughest questions with confidence. So, what are you waiting for? Start preparing today and take your career to the next level.
