Coding Interview Practice — How and What to Practice to Crack Coding Interviews

The coding interview is a prominent part of any technical interview at FAANG and other top tech companies. That’s why software engineers spend months practicing and preparing for this part of the interview process. 

Coding interviews are designed to test your proficiency in algorithms, data structures, and large-scale distributed systems. The level of difficulty of the coding problem will depend on the role you are interviewing for. Coding interviews are different in every company, so it’s important to have a general overview of the process, as well as do some research on the kind of questions asked by interviewers in different companies. Sounds like a lot of work, right? Well, that’s where we come in.

Having trained over 9,000 software engineers, coding engineers, and software developers, we at Interview Kickstart know what it takes to crack the toughest tech interviews. If you are preparing for a coding interview, check out our technical interview checklist, interview questions page to get interview-ready! Also, read the salary negotiation e-book for specific insights and guidance on the best ways to negotiate your compensation package in any interview.

In this article, we will cover the following:

• FAANG Coding Interview Process
• How to Practice for Coding Interviews
• Coding Interview Questions for Practice
• Frequently Asked Questions About Coding Interviews

FAANG Coding Interview Process

You are most likely to face coding assessments in two types of rounds:

1. Technical Phone Screen Interview
2. On-site Interview (comprising 3-5 rounds of coding and other technical skill assessments)

The coding interview process for software engineers is mostly the same in all top tier-1 tech companies. The interview is conducted virtually and overseen by someone from a senior position in the company. You are given a coding problem to solve using a remote collaborative editor. While preparing for the coding interview, it would be best to practice coding problems on a whiteboard because auto-correcting features are not allowed during coding interviews.

For more information on how tech interviews at FAANG work, read Understanding Technical Interviews at FAANG and How to Crack Them.

How to Practice for Coding Interviews

To be able to crack a coding interview, practice is the key. However, FAANG and other top tech companies have several hundreds of questions in rotation to test software engineers, and they keep adding and updating the list. This makes it almost impossible to cover all interview problems or problems or questions. The chances of facing an unknown problem at the time of the interview are very high.

Plan Your Practice

It is essential to plan your coding practice in an organized way so that you can cover the maximum “types” of interview questions. Practicing in this manner during your technical interview preparation will help you develop methods of solving different kinds of problems. So even if you’ve never seen a problem, you will be able to derive a solution based on similar problems you’ve practiced. 

At Interview Kickstart, we have been diving into this ocean of coding problems for the past several years. We have organized and distilled the problems into a checklist of topics — to access this, check out the Technical Interview Checklist, which covers the must-learn coding topics and system design topics that you should be well-versed in.

Practice Mock Interviews

Practicing a variety of problems is the start. You may cover each type of problem and feel confident, but you might still fumble on the day of the interview.

This is because the actual interview environment is very different from practicing in the comfort of your home. Mock interviews are a must to get familiar with the pressure of the interview. You need to put yourself in a simulated interview environment and time yourself to get a sense of where you stand. 

You can do this with the help of friends or peers. However, the best way to do mock interviews is with actual hiring managers or tech leads. If you do not have such contacts in your network, consider joining Interview Kickstart — the best way to prepare for coding interviews. Our instructors are hiring managers and tech leads from FAANG and other top tech companies. You can practice mock interviews with the best in the business. Their feedback will give you a hiring manager perspective that you will not get elsewhere and take your prep to the next level.

Coding Interview Questions for Practice

Most of the coding problems given in FAANG interviews are based on data structures and algorithms. You can expect questions on the following topics at the interview:

• Arrays
• Trees
• Stacks
• Recursion
• Binary Search
• Insertion Sort
• Bubble Sort
• Selection Sort
• Breadth-First Search
• Dynamic Programming
• Divide and Conquer
• Stacks and Queues

Recommended Reading:  Top 10 Algorithms to Crack Coding Interviews

In the following sections, we’ve covered some of the most common coding interview questions (categorized by topic) that you can utilize while practicing for your next interview.

Coding Interview Practice Questions on Arrays

1. Given K sorted arrays arr, of size N each, merge them into a new array res, such that res is a sorted array. (Solution)
2. Given an array of numbers nums of size n, find an array of numbers products of size n, such that products[i] is the product of all numbers nums[j], where j != i. (Solution)
3. There are 2 sorted arrays arr and brr of size n and m, respectively. Write an algorithm to find the median of the array obtained after merging arrays arr and brr (i.e., array of length n + m). (Solution)
4. Given two arrays: 1) arr1 of size n, which contains n positive integers sorted in ascending order. 2) arr2 of size (2*n) (twice the size of first), which contains n positive integers sorted in the ascending order in its first half. The second half of this array arr2 is empty. (Empty elements are marked by 0). Write a function that takes these two arrays, and merges the first one into the second one, resulting in an increasingly sorted array of (2*n) positive integers. (Solution)
5. Find the minimum element in an array that has been sorted and rotated by an unknown pivot. (Solution)
6. You are given a sorted two-dimensional integer array arr of size r * c, where all the numbers are in non-decreasing order from left to right and top to bottom, i.e., arr[i][j]. Check if a given number x exists in arr or not.  Given an arr, you have to answer q such queries. (Solution)
7. Given two sorted arrays (sorted in non-descending order) as input, you need to complete the function intersectionOfArrays, which will return a new array containing elements that are present in both of the input arrays. (Solution)
8. Given a non-decreasing order sorted array, return two indices whose value from the array adds up to the given target value. The same element can not be used twice. (Solution)
9. Given N distinct integers in a sorted array, build a balanced binary search tree (BST).. (Solution)

Coding Interview Practice Questions on Trees

1. You are given the root node of a binary tree T. You need to modify that tree in place, transform it into the mirror image of the initial tree T. (Solution)
2. Write a function that returns the number of distinct binary search trees that can be constructed with n nodes. For this exercise, solve the problem using recursion first, even if you see some non-recursive approaches. (Solution)
3. Implement an iterator over a binary tree with integer values. (Solution)
4. Given the inorder and preorder traversal of a valid binary tree, you have to construct the binary tree. (Solution)
5. Given a binary tree, return all paths from the root to leaf. (Solution)
6. Given a binary tree, check if it is a binary search tree (BST). A valid BST does not have to be complete or balanced.  (Solution)
7. Write a program to find the lowest common ancestor of two nodes of a given binary tree “B” with unique values.
8. Given a binary tree “B” with unique values, write a program to find:  1. The longest consecutive sequence. 2. The length of the longest path comprising connected nodes with consecutive values.

Coding Interview Practice Questions on Stacks

1. You have to build a min stack. Min stack should support push, pop methods (as usual stack), as well as one method that returns the minimum element in the entire stack. (Solution)
2. Given a sequence of enqueue and dequeue operations, return a result of their execution without using a queue data structure. (Solution)

Coding Interview Practice Questions on Recursion

3. Given a binary tree, find its postorder traversal without using recursion. (Solution)
4. Check if the given string s is a palindrome or not, using recursion. (Solution)

Coding Interview Practice Questions on Sort

1. Given a 2D matrix mat of integers with n rows and m columns. Each row of the matrix contains m integers in ascending order, and also each column contains n integers in ascending order. Your task is to find the kth smallest element in the matrix mat. (Solution)
2. Given some balls of three colors arranged in a line, rearrange them such that all the red balls go first, then green, and then blue ones. Do rearrange the balls in place. A solution that simply counts colors and overwrites the array is not the one we are looking for. (Solution)
3. You are given an array of integers. You have to sort the array using the merge sort algorithm. (Solution)
4. Sort the given singly linked list in ascending order. You have to do it in-place (using only constant extra space). (Solution)
5. Given k singly-linked lists where each linked list is sorted in ascending order, merge all of them into a single sorted linked list. (Solution)

Other Coding Interview Questions for Practice

1. You’re given two strings, ‘S’ and ‘K.’ Write a program to find the longest common substring.
2. Find all palindromic decompositions of a given string s. (Solution)
3. Given a variety of coin types defining a currency system, find the minimum number of coins required to express a given amount of money. Assume an infinite supply of coins of every type. (Solution)
4. Sort a given singly linked list in ascending order. (Solution)
5. Write a code to convert a given set of integers into their Roman number equivalents. 
6. Write a program to find out if a given number “N” is sparse. (A number is said to be sparse if no two bits are in binary representation).
7. Given a list of meeting time intervals consisting of start and end times [[s1, e1], [s2, e2], ...] (si < ei). You need to complete canAttendAllMeetings function and return 1 if a person can attend all given meetings else 0.
8. Given a string s containing a set of words, transform it such that the words appear in the reverse order. Words in s are separated by one or more spaces.
9. Given a sequence, return its next lexicographically greater permutation. If such a permutation does not exist, then return it in ascending order. 
10. Try to solve the problem with a constant amount of additional memory.
11. You are given alphanumeric strings s and t. Find the minimum window (substring) in s, which contains all the characters of t.
12. Given ‘n’ pairs of numbers where: In each pair, the first number is smaller than the second number. If c<f, a certain pair [a,b] takes numbers from two different pairs [c,d] and [e,f].
13. Write a program to find the longest subsequence in two given strings, ‘str1’ and ‘str2’. 

For more coding interview practice questions, check out:

• Google Coding Interview Practice Questions
• Amazon Coding Interview Practice Questions
• Facebook Coding Interview Practice Questions

Frequently Asked Questions About Coding Interviews

Q. Is it OK to change programming languages midway during the coding interview?

A. Yes, it is okay to change your programming language during the interview. However, make sure that you justify your decision to the interviewers. It is a good practice to think out loud during the interview so that the interviewers understand your thought process. 

Q. What is the best way to prepare for a coding interview?

A. Coding practice for interviews takes a solid action plan. You can sign up for a technical interview preparation course, where experts will guide you through the technical interview process at FAANG companies. Interview Kickstart is the best way to practice coding interview questions.

Crack Your Next Coding Interview 

If you’re looking for guidance and help with getting your prep started, sign up for our free webinar. As pioneers in the field of technical interview preparation, we have trained thousands of software engineers, coding engineers, and software developers to crack the most challenging coding interviews and land jobs at their dream companies, such as Google, Facebook, Apple, Netflix, Amazon, and more!

That’s not all. We offer 17 domain-specific technical interview preparation courses, covering the most in-demand skills in the tech industry. 

Sign up now for our FREE webinar to learn more about how our courses can help you uplevel.