Interview coding challenges for developers often play a crucial role in helping hiring managers select candidates with the right set of skills and a strong understanding of the key technical principles. FAANG and other top tech companies use interview coding challenges to hire the best talent. The questions in these coding challenges test your DSA (Data Structure and Algorithms) knowledge. However, the questions are pretty tricky, and you’re expected to use your technical skills and creativity to solve them.
Preparing for coding challenges can accelerate your problem-solving ability, enhance your skills, and boost your confidence. Every software developer has to face coding challenges in technical interviews. Let’s take a look at the types of coding challenges asked in FAANG+ interviews and how you can solve them.
In this article, we will answer questions like why big companies use interview coding challenges to interview developers, what coding challenges are, and how to solve coding challenges in an interview in this article.
What Are Coding Interview Challenges?
Interview coding challenges or hiring coding challenges are tests that companies use to screen the technical skills and coding proficiency of potential candidates. Coding interview challenges include brainteasers, business problems, coding tests, and behavioral questions.
For software engineers, the focus is on coding problems. They can precede or follow phone and in-person technical interviews or be a separate event from the interview.
To stand a good chance at solving problems in coding challenges, you must brush up on the following:
- Arrays, stacks, and linked lists
- Recursion
- Sorting algorithms
- Trees and graphs
- Hash tables
- Graph algorithms
- Dynamic programming
Why Do Companies Use Interview Coding Challenges to Interview Developers?
Interview coding challenges as a part of the interview process offer multiple benefits. Besides simply testing your abilities, the discernible features of an interview code challenge make it better than just any traditional interview:
- Live coding processes, where you have to solve a problem in the interviewer’s presence, help them understand how you code. They get an insight into how you think about the problem.
- Coding challenges put potential employees in an environment similar to the workplace.
- Giving candidates real-world problems to solve reflects how well they will do on the job and how they would impact the company.
- It provides a sample of your quality of work in a condensed presentation.
- It offers big companies a more credible and effective way to understand your skills than they would by merely talking to you.
- It helps hiring managers in making hiring decisions. Based on their observations, they can figure out the right position for you and estimate which skills they will have to hone.
What Are the Different Types of Interview Coding Challenges for Jobs?
Recruiters follow one of these five ways to assign coding challenges in interviews:
Open Coding Challenges
Many tech companies conduct open coding challenges. These are tech events that invite programmers worldwide to participate, solve coding problems, and win rewards for finishing on top. For instance, Google conducts three coding challenges every year.
Amazon also hires candidates through coding challenges on HackerEarth and TechGig throughout the year. You can learn some tips to crack Amazon coding challenge.
Take-home Coding Challenges
Here, the recruiter emails the coding challenges, and you can solve them at your convenience but within the deadline. The take-home interview coding challenge is an efficient way to check candidates’ problem-solving skills and knowledge as they get the time and space just like an employee.
Pair Programming
In this interview coding challenge, you solve the problems by coordinating with the interviewer. Pair programming is usually applicable to senior programming candidates.
Whiteboarding
Whiteboard tests help recruiters assess your ability to manage stressful situations. Here, you have to solve the interview code challenge problem on a whiteboard in the recruiter’s presence.
Screening Questions
It consists of quiz-like coding challenges. These are pretty short, so they are not precisely full-fledged coding challenges. However, screening questions work well when big companies have too many applicants.
Sample Interview Coding Challenges and Solutions
The best advice to ace a coding test is to practice as many coding problems as possible. You must participate in open coding events. For interviews, although coding challenges differ for every company, here are a few samples of some of the most popular languages and frameworks.
Python Coding Interview Challenges
Here are a few python interview coding challenges:
1. Given a list of numbers, write a program using Python to convert every item of a list into its square
def square_elements(lst):
return [x**2 for x in lst]
# Example usage
numbers = [1, 2, 3, 4, 5]
print(square_elements(numbers)) # Output: [1, 4, 9, 16, 25]
2. Swap two tuples in Python
def swap_tuples(tup1, tup2):
return tup2, tup1
# Example usage
tuple1 = (1, 2)
tuple2 = (3, 4)
tuple1, tuple2 = swap_tuples(tuple1, tuple2)
print(“Tuple1:”, tuple1) # Output: Tuple1: (3, 4)
print(“Tuple2:”, tuple2) # Output: Tuple2: (1, 2)
3. Use Python to write a program that returns a list containing only the common elements between two lists. Ensure that the list is without duplicates and that your program works on both lists.
The lists are: x = [1, 1, 2, 3, 5, 9, 13, 14, 34, 55, 89] and y = [1, 2, 3, 4, 5, 6, 7, 8, 9, 11, 15, 22, 54]
def common_elements(list1, list2):
return list(set(list1) & set(list2))
# Example usage
x = [1, 1, 2, 3, 5, 9, 13, 14, 34, 55, 89]
y = [1, 2, 3, 4, 5, 6, 7, 8, 9, 11, 15, 22, 54]
print(common_elements(x, y)) # Output: [1, 2, 3, 5, 9]
4. Create a Morse code translator in Python.
Take in a string with alphanumeric characters in lower or upper case. The string can also contain any special characters handled in Morse code. The function should return the Morse code equivalent for the string
MORSE_CODE_DICT = {
‘A’: ‘.-‘, ‘B’: ‘-…’, ‘C’: ‘-.-.’, ‘D’: ‘-..’, ‘E’: ‘.’, ‘F’: ‘..-.’, ‘G’: ‘–.’, ‘H’: ‘….’,
‘I’: ‘..’, ‘J’: ‘.—‘, ‘K’: ‘-.-‘, ‘L’: ‘.-..’, ‘M’: ‘–‘, ‘N’: ‘-.’, ‘O’: ‘—‘, ‘P’: ‘.–.’,
‘Q’: ‘–.-‘, ‘R’: ‘.-.’, ‘S’: ‘…’, ‘T’: ‘-‘, ‘U’: ‘..-‘, ‘V’: ‘…-‘, ‘W’: ‘.–‘, ‘X’: ‘-..-‘,
‘Y’: ‘-.–‘, ‘Z’: ‘–..’, ‘0’: ‘—–‘, ‘1’: ‘.—-‘, ‘2’: ‘..—‘, ‘3’: ‘…–‘, ‘4’: ‘….-‘,
‘5’: ‘…..’, ‘6’: ‘-….’, ‘7’: ‘–…’, ‘8’: ‘—..’, ‘9’: ‘—-.’, ‘&’: ‘.-…’, “‘”: ‘.—-.’,
‘@’: ‘.–.-.’, ‘)’: ‘-.–.-‘, ‘(‘: ‘-.–.’, ‘:’: ‘—…’, ‘,’: ‘–..–‘, ‘=’: ‘-…-‘, ‘!’: ‘-.-.–‘,
‘.’: ‘.-.-.-‘, ‘-‘: ‘-….-‘, ‘+’: ‘.-.-.’, ‘”‘: ‘.-..-.’, ‘?’: ‘..–..’, ‘/’: ‘-..-.’
}
def to_morse_code(text):
return ‘ ‘.join(MORSE_CODE_DICT.get(char.upper(), ”) for char in text)
# Example usage
print(to_morse_code(“Hello, World!”))
5. Find the domain namee using an IP address. You can import the Python socket library
import socket
def get_domain(ip_address):
try:
return socket.gethostbyaddr(ip_address)[0]
except socket.herror:
return “Domain not found”
# Example usage
ip = “8.8.8.8”
print(get_domain(ip)) # Output may vary based on the IP address provided
6. Write a function in Python that accepts a string of ASCII characters. It must return each character’s value as a hexadecimal string. You must separate each byte by a space and return all alpha hexadecimal characters as lowercase
def ascii_to_hex(string):
return ‘ ‘.join(format(ord(char), ’02x’) for char in string)
# Example usage
print(ascii_to_hex(“Hello World”)) # Output: “68 65 6c 6c 6f 20 77 6f 72 6c 64”
7. Using Python, create a function that accepts one parameter: a string that is a sentence. This function should return True if the sentence has a word containing duplicate letters and False if not.
def has_duplicate_letter_word(sentence):
words = sentence.split()
for word in words:
if len(set(word)) != len(word):
return True
return False
# Example usage
print(has_duplicate_letter_word(“This sentence has no duplicates”)) # Output: False
print(has_duplicate_letter_word(“This sentence has a duplicate”)) # Output: True
Practice some more Advanced Python Coding Challenges here!
Java Coding Challenges
Here are a few Java interview coding challenges:
1. Given a string S, return the “reversed†string. All letters will reverse their positions, and characters that are not a letter stay in the same place
public class ReverseString {
public static String reverseOnlyLetters(String s) {
char[] arr = s.toCharArray();
int left = 0, right = arr.length – 1;
while (left < right) {
if (!Character.isLetter(arr[left])) {
left++;
} else if (!Character.isLetter(arr[right])) {
right–;
} else {
char temp = arr[left];
arr[left] = arr[right];
arr[right] = temp;
left++;
right–;
}
}
return new String(arr);
}
public static void main(String[] args) {
String s = “a-bC-dEf-ghIj”;
System.out.println(reverseOnlyLetters(s)); // Output: “j-Ih-gfE-dCba”
}
}
2. Create a Java program to reverse a string. Do not use the reverse method of Java’s String class
public class ReverseStringNoMethod {
public static String reverse(String s) {
StringBuilder reversed = new StringBuilder();
for (int i = s.length() – 1; i >= 0; i–) {
reversed.append(s.charAt(i));
}
return reversed.toString();
}
public static void main(String[] args) {
String s = “hello”;
System.out.println(reverse(s)); // Output: “olleh”
}
}
3. Write a phone number word decoder. Write a Java program that will accept a contact number with letters and convert it to a contact number with digits only
public class PhoneDecoder {
public static String decodePhoneNumber(String input) {
StringBuilder decoded = new StringBuilder();
for (char ch : input.toCharArray()) {
if (Character.isDigit(ch)) {
decoded.append(ch);
} else {
decoded.append(getNumberForChar(ch));
}
}
return decoded.toString();
}
private static int getNumberForChar(char ch) {
ch = Character.toUpperCase(ch);
if (“ABC”.indexOf(ch) != -1) return 2;
if (“DEF”.indexOf(ch) != -1) return 3;
if (“GHI”.indexOf(ch) != -1) return 4;
if (“JKL”.indexOf(ch) != -1) return 5;
if (“MNO”.indexOf(ch) != -1) return 6;
if (“PQRS”.indexOf(ch) != -1) return 7;
if (“TUV”.indexOf(ch) != -1) return 8;
if (“WXYZ”.indexOf(ch) != -1) return 9;
return -1; // Unknown character
}
public static void main(String[] args) {
System.out.println(decodePhoneNumber(“1-800-FLOWERS”)); // Example output: “1-800-3569377”
}
}
4. Write code to design a vending machine
public class VendingMachine {
private static VendingMachine instance;
private int balance;
private VendingMachine() {
this.balance = 0;
}
public static VendingMachine getInstance() {
if (instance == null) {
instance = new VendingMachine();
}
return instance;
}
public void insertMoney(int amount) {
balance += amount;
System.out.println(“Inserted money: $” + amount);
}
public void selectProduct(int price) {
if (balance >= price) {
balance -= price;
System.out.println(“Product dispensed. Remaining balance: $” + balance);
} else {
System.out.println(“Insufficient balance.”);
}
}
public int getBalance() {
return balance;
}
public static void main(String[] args) {
VendingMachine vm = VendingMachine.getInstance();
vm.insertMoney(5);
vm.selectProduct(3);
}
}
5. Write a Java program that returns an MD5 hash
import java.security.MessageDigest;
import java.security.NoSuchAlgorithmException;
public class MD5Hash {
public static String getMD5(String input) {
try {
MessageDigest md = MessageDigest.getInstance(“MD5”);
byte[] messageDigest = md.digest(input.getBytes());
StringBuilder sb = new StringBuilder();
for (byte b : messageDigest) {
sb.append(String.format(“%02x”, b));
}
return sb.toString();
} catch (NoSuchAlgorithmException e) {
throw new RuntimeException(e);
}
}
public static void main(String[] args) {
System.out.println(getMD5(“Hello World”)); // Example output: “fc3ff98e8c6a0d3087d515c0473f8677”
}
}
6. Create a Java Singleton class
public class Singleton {
private static Singleton instance;
private Singleton() {}
public static Singleton getInstance() {
if (instance == null) {
instance = new Singleton();
}
return instance;
}
public void showMessage() {
System.out.println(“Hello from Singleton!”);
}
public static void main(String[] args) {
Singleton singleInstance = Singleton.getInstance();
singleInstance.showMessage();
}
}
7. Print all permutations of String in both iterative and Recursive ways
public class StringPermutations {
public static void permuteRecursive(String str, String answer) {
if (str.length() == 0) {
System.out.println(answer);
return;
}
for (int i = 0; i < str.length(); i++) {
char ch = str.charAt(i);
String ros = str.substring(0, i) + str.substring(i + 1);
permuteRecursive(ros, answer + ch);
}
}
public static void main(String[] args) {
permuteRecursive(“ABC”, “”);
}
}
8. Given an array of size N, sort the array elements by completing functions heapify() and buildHeap() to implement Heap Sort
public class HeapSort {
public void heapify(int arr[], int n, int i) {
int largest = i;
int left = 2 * i + 1;
int right = 2 * i + 2;
if (left < n && arr[left] > arr[largest]) largest = left;
if (right < n && arr[right] > arr[largest]) largest = right;
if (largest != i) {
int swap = arr[i];
arr[i] = arr[largest];
arr[largest] = swap;
heapify(arr, n, largest);
}
}
public void buildHeap(int arr[], int n) {
for (int i = n / 2 – 1; i >= 0; i–) {
heapify(arr, n, i);
}
}
public void heapSort(int arr[]) {
int n = arr.length;
buildHeap(arr, n);
for (int i = n – 1; i >= 0; i–) {
int temp = arr[0];
arr[0] = arr[i];
arr[i] = temp;
heapify(arr, i, 0);
}
}
public static void main(String[] args) {
int arr[] = {12, 11, 13, 5, 6, 7};
HeapSort hs = new HeapSort();
hs.heapSort(arr);
for (int num : arr) {
System.out.print(num + ” “);
}
}
}
React Coding Challenges
React is a popular front-end web framework. The interview coding challenges are used for a React developer to check your experience. Interviewers expect you to understand the coding problem quickly and solve it in an organized way.
Here are a few React coding challenges for practice:
1. Add and delete items from the list: Create an input field with a button. On clicking the button, the text in the input field should be added below in a list. Also, when any list item is clicked, it should be removed from the list
import React, { useState } from “react”;
function App() {
const [input, setInput] = useState(“”);
const [items, setItems] = useState([]);
const handleAddItem = () => {
if (input) {
setItems([…items, input]);
setInput(“”); // Clear input field after adding
}
};
const handleRemoveItem = (index) => {
setItems(items.filter((_, i) => i !== index));
};
return (
<div>
<input
type=”text”
value={input}
onChange={(e) => setInput(e).target.value)}
placeholder=”Enter item”
/>
<button onClick={handleAddItem}>Add Item</button>
<ul>
{items.map((item, index) => (
<li key={index} onClick={() => handleRemoveItem(index)}>
{item}
</li>
))}
<ul>
<div>
);
}
export default App;
Here:
- the handleAddItem function adds the input to the list when the button is clicked
- the handleRemoveItem function removes an item when it is clicked on the list
Displaying data coming from an API: In this challenge, you will be given an API that will return some data. This may be an array of objects. You have to display the data in the UI
import React, { useState, useEffect } from “react”;
function App() {
const [data, setData] = useState([]);
useEffect(() => {
const fetchData = async () => {
try {
const response = await fetch(“https://api.example.com/data”); // Replace with actual API URL
const result = await response.json();
setData(result);
} catch (error) {
console.error(“Error fetching data:”, error);
}
};
fetchData();
}, []);
return (
<div>
<h1>Data from API</h1>
<ul>
{data.map((item, index) => (
<li key={index}>{JSON.stringify(item)} // Customize how data is displayed
))}
<ul>
</div>
);
}
export default App;
In this code:
- fetchData is an asynchronous function that fetches data from the API when the component mounts
- Data is then displayed in a list
3. Write code to re-render the view when thee browser is resized
import React, { useState, useEffect } from “react”;
function App() {
const [width, setWidth] = useState(window.innerWidth);
useEffect(() => {
const handleResize = () => setWidth(window.innerWidth);
window.addEventListener(“resize”, handleResize);
// Clean up event listener on component unmount
return () => window.removeEventListener(“resize”, handleResize);
}, []);
return (
<div>
<h1>Current window width: {width}px</h1>
<div>
);
}
export default App;
Explanation:
- The handleResize function updates the state with the window’s current width
- The component re-renders each time the width state changes
4. Write code to pass data between sibling components using React router
To pass data between sibling components in React, you can use React Router’s useLocation or useParams to pass props via URL parameters. Here’s a simple setup.
Setup
1. Install react-router-dom if it’s not already installed
npm install react-router-dom
App.js
import React from “react”;
import { BrowserRouter as Router, Route, Link, Routes } from “react-router-dom”;
import PageOne from “./PageOne”;
import PageTwo from “./PageTwo”;
function App() {
return (
<Router>
<div>
<nav>
<Link to=”/page1>Page 1</Link>
<Link tp=”/page2>Page 2</Link>
</nav>
<Routes>
<Route path=””/page1″ element={<PageOne />} />
<Route path=”/page2″ element={<PageTwo />} />
</Routes>
</div>
<Router>
);
}
export default App;
Netflix Coding Challenges
Netflix seeks developers who could display their content in innovative ways. Here are a few examples of Netflix interview coding challenge questions:
-
- Improve search results by enabling users to see relevant search results without being hindered by typos. This will be called the “Group Similar Titles†feature.
- Given an array of integers and a value, you have to determine whether there are any three integers in the array whose sum equals the given value.
- Given the head nodes of two linked lists that may or may not intersect, you have to determine if they intersect and return the point of intersection. Else return null.
- Convert binary tree into a doubly-linked list.
- Given a sentence, reverse words’ order.
- Print all braces combinations for a given value n, so they are balanced.
- Serialize a binary tree to file and deserialize it back to a tree.
- Search for a given number in a sorted rotated array by some arbitrary number. Return -1 if the number does not exist. Assumption- the array does not contain duplicates.
IBM also conducts coding challenges through third-party websites like HackerRank, HackerEarth, and TechGig. Sometimes, these coding challenges are a preliminary round for your IBM interview. Learn some tips to nail the IBM coding challenge.
Top Websites to Practice Coding Challenges for Hiring
There are popular websites that offer coding challenges for practice. Apart from these websites, you can also participate in coding competitions or contests to test your coding skills. International The Collegiate Programming Contest (ICPC) is a well-known competitive programming competition. These coding challenges will help you showcase your programming skills in your FAANG interview.
These are the most popular websites where you can practice coding challenges:
- HackerRank
- LeetCode
- TopCoder
- Coderbyte
- CodeChef
- Project Euler
- Exercism.io
- Codewars
- CodinGame
- Codeforces
- SPOJ
Practicing coding challenge problems and more will help you improve problem-solving and gain confidence for your next tech interview. You can check out our problems page for more questions.
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FAQs: Coding Interview Challenges
Q1. How important are solving code challenges during the interview process?
Solving interview coding challenges is a crucial part of your interview process. All major tech companies include tricky coding questions to test your coding skills and knowledge of programming languages.
Q2. How can I crack coding challenges?
To crack a coding challenge in an interview, you must thoroughly understand data structures and algorithms and different coding languages and their application. You must practice solving numerous coding challenges to get fluent in applying the codes.
Q2. Does solving coding challenges help to crack a job interview?
Yes, the more coding challenges you solve, your work gets more efficient. Many big companies evaluate your coding and problem-solving skills by challenging tricky coding. It is a crucial part of the recruitment process.
Q3. Can coding challenges make me a better programmer?
Coding challenges are designed to challenge your ability to solve a problem. They make you an efficient and smart programmer in the most fun way.
Q4. Why are coding interview challenges important for tech interviews?
Coding interview challenges are essential because they help interviewers assess candidates’ technical skills and problem-solving abilities in real-world scenarios. They reveal how well a candidate can think and code under pressure.
Q5. How should I prepare for coding interview challenges in FAANG interviews?
To prepare for coding interview challenges, focus on mastering data structures and algorithms. Practice coding problems regularly on sites like LeetCode, HackerRank, and CodeSignal to build speed and confidence.
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