# Must-Do Coding Interview Questions for Product Based Companies

## Introduction

Preparing for the hiring process of big __product-based companies__ from Google to Microsoft requires an endless amount of practicing of problems. These interviews are deemed to be very hard to crack but hold the dreams of many budding software developers.

Well, this can be intimidating! But the good news is that most of them have a defined structure going on from previous years. So the kind of questions that are posed can be predicted after an analysis of last year’s trends and patterns.

Attempts at such analysis have shown that product-based companies essentially focus on evaluating your skills in Data Structures and Algorithms. Understanding why it is so is necessary before we dive into the list of coding interview questions from this topic. We will look at this in the coming section.

## Why the focus on DSA?

Let’s look at some of the reasons why Data Structures and Algorithms is a significant area of evaluating candidates in interviews with big product-based companies.

**Optimal usage of time and memory**: Companies like__Google__and__Facebook__that have a large number of users spread around the world with even more significant amounts of data require that all of this data be taken care of in the most optimal manner. The ability to do this can only be achieved if a programmer has good skills in Data Structures and Algorithms.

**Assessment of problem-solving skills**: DSA is a topic that effectively tests a candidate’s ability to analyze problems and derive solutions to them spontaneously. Thus, making it an excellent parameter to assess an individual’s problem-solving skills.

**Real-life applications**: The applications of data structures in real life are very evident for anyone familiar with the topic. Knowing how computer science concepts are applied and valuable in our daily lives is something that a lot of recruiters indirectly look for.

## Topic-wise must-do Coding Interview Questions

Since we now know how important it is to master data structures, let’s look at a roadmap of various topics that you need to master, based on an analysis by Parikh Jain, a founding member and instructor at __Coding Ninjas__.

So here is a compilation of all the must-do coding interview questions sorted topic-wise for your convenience in one place! Make full use of it!

## Arrays for Coding Interview Questions

The topic to start with is Arrays. An array is a linear data structure with a predefined size in which elements are stored in contiguous blocks of memory. An array can be one-dimensional or multidimensional. Multidimensional arrays need to be studied separately and find their best application in Matrices.

Below is a list of important coding interview questions from this topic. Click on any question to start practising and understanding right away!

- Arrays
- Multi-Dimensional Arrays

## Strings for Coding Interview Questions

An array that consists of characters as elements is called a string. What makes it different from a character array is that it ends with a special symbol ‘\0’.

Below are a few important questions from this topic.

__Longest Substring Without Repeating Characters____Anagram Difference____Shortest substring with all characters____Minimum operations to make strings equal____Other Questions Practice Link__

## Recursion & Backtracking for Coding Interview Questions

__Recursion__ is a technique in programming in which a function is called by itself directly or indirectly. It is used to solve complex problems by breaking them into smaller problems. On the other hand, backtracking is a technique that uses __recursion__ to build an overall solution by incrementally going through smaller levels of the problem until the solution is reached. Given are some questions that you must practice from this topic before going for an interview.

__Print Permutations Of String____Return Subsets Sum to K____Sudoku____Replace ‘O’ with ‘X’____Reach Destination____Other Questions Practice link__

## Linked Lists for Coding Interview Questions

Linked List is a dynamic linear data structure that consists of nodes where each node consists of two fields – data and pointer. Each node points towards the next node. The first node is called Head that points to the second node and so on. It is of three types – Singly Linked List, Doubly Linked List and Circular Linked List.

__Merge Two Sorted Linked List____Detect And Remove Loop____Reverse List In K Groups____Intersection Of Two Linked List____Sum Between Zeros____Other Questions Practice Link__

## Stacks & Queues for Coding Interview Questions

The arrangement of data in stacks and queues is as their names suggest. In a stack, a visual representation of its data can be seen as one element on top of the other, working on the First In Last Out (FILO) Principle. In a queue, on the other hand, elements are put one after the other, working on the First In First Out (FIFO) principle.

__Implement Stack Using Linked List____Next Greater Element____Implement Queue Using Stack____LRU Cache Implementation____Evaluation Of Postfix Expression____Other Questions Practice Link__

## Binary Trees for Coding Interview Questions

A Binary Tree is a tree in which each node consists of at most two children. Each node consists of three fields – data, a pointer to the left child, and a pointer to the right child. Must-do questions for coding interviews from Binary Tree are given below:

__Binary Tree From Parent Array____Maximum Sum Path From Root To Leaf____Print Node At Distance K From Given node____Maximum Width In Binary Tree____Time To Burn Tree____Other Questions Practice Link__

## Binary Search Tree for Coding Interview Questions

A Binary Search Tree is a sorted binary tree in which the left subtree of a node consists of values lesser than the value of that node, and the right subtree consists of those greater. Here are some must-do questions on this topic.

__Delete In BST____Sorted Linked List To Balanced BST____Kth Smallest Element In BST____Binary Tree To BST____Pair Sum in BST____Other Questions Practice Link__

## Priority Queues & Heaps

A priority queue is a queue in which every value is associated with a priority. Dequeuing takes place in a manner that the element with a higher priority is dequeued before an element with a lower priority. Heaps are a special type of data structure which are based on complete binary trees. They are of two types – Min heap and Max heap. After an analysis,

__Running Median____Convert Min Heap To Max Heap____Kth Largest Element In Unsorted Array____K Most Frequent Words____Last Stone Weight____Other Questions Practice Link__

## Graphs for Coding Interview Questions

A Graph is a non-linear data structure that consists of nodes and edges. A node is a vertex and an edge is a line or curve that connects any two vertices. Some important problems for coding interviews from this topic are given below:

__Is Graph A Tree?____M Coloring Problem____Snake And Ladder____Shortest Path In Unweighted Graph____Alien Dictionary____Other Questions Practice Link__

## Dynamic Programming for Coding Interview Questions

Dynamic Programming is an optimisation technique working on recursion in which we divide a complex problem into smaller subproblems. It finds many applications in computer science. Must-do problems from this topic are linked as follows:

__Edit Distance____Rod Cutting Problem____Longest Palindromic Substring____Knapsack____Palindrome Partitioning____Other Questions Practice Link__

## Other Important for Coding Interview Questions

Apart from the questions categorised above in the form of topics, we have compiled a list of more coding interview questions that you must practice before appearing for any tech interview.

__Implement Hashmap____Implement Trie____Implement Deque____Other Questions Practice Link__- Reserve a
__string in C++__and__C__

## Frequently Asked Questions

**What should I study for a coding interview?**

Before you start practicing coding for an interview, you must be familiar with aspects the particular company’s interview focuses on. For product based companies, you must practice data structures and algorithms, while for service-based companies, you should focus on your software development skills.

**How do I practice coding for an interview?**

After you have knowledge about what kind of questions you need to solve, you must immediately start working on coding the problems that are known to be the most important ones. CodeStudio is the perfect platform to help you get a guided path on how to do this.

**How do you code a question?**

Before you jump to coding the answer to a question, you must first understand the question, secondly make test cases, and thirdly do a dry run. Then you should develop a pseudocode which would make it easier for you to develop the final code.

**How do I start coding?**

The first step to starting coding is to learn a programming language that will be the medium for you to communicate with the computer. Which programming language to choose can be based on your future interests, or if not, you can choose any programming language you want because it is merely a medium.

**How do beginners practice coding?**

Beginners should develop a solid foundation by learning one programming language to start and then moving to solve problems in that language to build their problem-solving skills.

**How many hours a day should you practice coding?**

The number of hours required varies from person to person. The important thing is to devote more hours to get stronger in a weak topic and less in reviewing mastered topics. Consistency is key.

**How can I practice coding every day?**

You can practice coding every day by keeping a fixed number of questions to solve every day. Another way can be to set the number of hours.

**Where can I practice coding questions?**

There are various platforms that give you a pool of problems to solve, like CodeChef, Hackerrank, CodeStudio, and LeetCode.

## Conclusion

In this article, we started with a discussion on how being familiar with certain types of questions gives you a boost to qualify for a job at big product-based companies.

Then we shed light on why and how data structures and algorithms are the most important topics to master to help you get through any tech interview in product-based companies. Finally, we presented our whole list of questions from all topics of data structures that any candidate aspiring to crack the interviews of big product based companies must master.

After reading this blog, are you not feeling excited to read/explore more articles on the Interview related topics? Don't worry; Coding Ninjas has you covered. To learn, see __Production Support Interview Questions__.