Top 10 Coding Questions Asked in Product-Based Companies

Here’s a list of the top 10 coding questions commonly asked in product-based companies, along with a brief explanation of each, tailored for a technical interview setting. These companies typically look for strong problem-solving skills, algorithmic understanding, and coding proficiency.

1. Reverse a Linked List

• Problem: Given a singly linked list, reverse the list and return the new head node.
• Concepts Tested: Linked lists, pointers, iterative vs recursive approaches.
• Example: Reverse the linked list 1 -> 2 -> 3 -> 4 -> 5 to 5 -> 4 -> 3 -> 2 -> 1.

2. Find the Middle Element of a Linked List

• Problem: Given a linked list, find the middle element. If there are two middle elements, return the second one.
• Concepts Tested: Linked lists, fast and slow pointers, traversal techniques.
• Example: For 1 -> 2 -> 3 -> 4 -> 5, return 3.

3. Merge Two Sorted Arrays

• Problem: Given two sorted arrays, merge them into a single sorted array.
• Concepts Tested: Arrays, merging, time and space complexity.
• Example: Merge [1, 3, 5] and [2, 4, 6] to form [1, 2, 3, 4, 5, 6].

4. Detect Cycle in a Linked List

• Problem: Given a linked list, determine if it contains a cycle.
• Concepts Tested: Linked lists, Floyd’s Tortoise and Hare algorithm, cycle detection.
• Example: For a list where node 3 points back to node 1, return True.

5. Longest Substring Without Repeating Characters

• Problem: Given a string, find the length of the longest substring without repeating characters.
• Concepts Tested: Sliding window technique, hash maps.
• Example: For the string “abcabcbb”, the longest substring is “abc”, with a length of 3.

6. Find the Kth Largest Element in an Array

• Problem: Given an unsorted array, find the kth largest element.
• Concepts Tested: Sorting, heap data structures, quickselect algorithm.
• Example: In the array [3, 2, 1, 5, 6, 4], the 2nd largest element is 5.

7. Two Sum

• Problem: Given an array of numbers and a target sum, return the indices of the two numbers that add up to the target.
• Concepts Tested: Hash maps, arrays, optimization.
• Example: For nums = [2, 7, 11, 15] and target = 9, return [0, 1] as 2 + 7 = 9.

8. Valid Parentheses

• Problem: Given a string containing just the characters ‘(‘, ‘)’, ‘{‘, ‘}’, ‘[‘ and ‘]’, determine if the input string is valid. An input string is valid if:
  • The brackets must close in the correct order.
  • The brackets must be balanced.
• Concepts Tested: Stacks, string manipulation.
• Example: For input "{[()]}", return True. For input "([)]", return False.

9. Permutations of a String

• Problem: Given a string, return all possible permutations of the string.
• Concepts Tested: Backtracking, recursion.
• Example: For input "abc", the permutations would be ["abc", "acb", "bac", "bca", "cab", "cba"].

10. Finding the Lowest Common Ancestor in a Binary Tree

• Problem: Given a binary tree and two nodes, find their lowest common ancestor (LCA).
• Concepts Tested: Trees, recursion, path tracking.
• Example: In a binary tree, if the nodes are 5 and 1, the LCA is 3.

Key Skills Tested:

• Data Structures: Most of these questions test your understanding of core data structures like arrays, linked lists, stacks, queues, trees, and graphs.
• Algorithms: You’ll need to show proficiency with sorting, searching, dynamic programming, and graph traversal algorithms.
• Problem-Solving: A product-based company is interested in how you approach a problem, break it down, and optimize your solution for time and space complexity.

Tips for Preparation:

• Practice coding problems on platforms like LeetCode, HackerRank, and CodeSignal.
• Understand the time complexity of your solution (Big O notation) and optimize where possible.
• Familiarize yourself with common data structures and their operations.
• Develop a strong foundation in recursion and backtracking techniques.

By consistently practicing these types of problems, you’ll be well-prepared for coding interviews at product-based companies.

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