TikTok IOS Developer Interview Questions and Answers

Q1. Find the possible ways to get the target score
Ans. 
There are multiple ways to achieve the target score in a game or competition.
• Incrementing by 1 point each time until reaching the target score

• Combining different point values to reach the target score

• Using bonus points or multipliers to reach the target score
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Round duration - 90 minutes
Round difficulty - Hard

Online coding round , 2-3 questions. Level - med-hard

Q1. 
Fibonacci Number Verification
Identify if the provided integer 'N' is a Fibonacci number.
A number is termed as a Fibonacci number if it appears in the Fibonacci sequence, where each number is the sum of...read more
Ans. 
Check if a given number is a Fibonacci number or not.
• Iterate through the Fibonacci sequence until you find a number greater than or equal to the given number.

• Check if the given number matches the Fibonacci number found in the sequence.

• If the given number matches, output 'YES'; otherwise, output 'NO'.
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Q2. 
Break The Board Problem Statement
Your task is to break a board of given dimensions 'L' by 'W' into 'L' * 'W' smaller squares, ensuring the total cost of breaking is minimized.
Input:
The first line con...read more
Ans. 
Minimize cost of breaking a board into smaller squares by optimizing horizontal and vertical cuts.
• Iterate through all possible horizontal and vertical cuts to find the minimum cost

• Use dynamic programming to store and reuse subproblem solutions

• Calculate the cost of breaking the board into smaller squares based on the given dimensions and cut costs
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Round duration - 60 Minutes
Round difficulty - Medium

2 interviewers , coding problem, no compilation.

Q1. 
Minimum Number Of People To Teach
Ninja has started a social networking site called Ninjas Space. The platform consists of ‘N’ users and supports ‘M’ different languages. Users communicate if they know at...read more
Ans. 
Determine the minimum number of users to teach a common language so all friends can communicate on a social networking site.
• Create a graph where users are nodes and friendships are edges.

• Find connected components in the graph.

• For each connected component, determine the minimum number of users to teach a common language.

• Return the sum of minimum users needed for all connected components.
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Round duration - 40 minutes
Round difficulty - Medium

CS fundamentals. Tough round. 40 mins interview. 1 interviewer from USA

Round duration - 40 minutes
Round difficulty - Hard

System Design Problem

Q1. Design a Facebook-like application.
Ans. 
Design a Facebook-like application for social networking.
• User profiles with personal information and photos

• News feed displaying posts from friends

• Ability to like, comment, and share posts

• Friend requests and messaging functionality

• Groups and events for community engagement
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Leetcode similar coding tests

Q1. How do you test the feasibility of an idea?
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Q2. Explain the process of calling an API
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DSA round was there it was good

Q1. Why you want to join facebook?
Ans. 
I want to join Facebook because of its innovative technology, global impact, and opportunities for growth.
• Innovative technology: Facebook is known for its cutting-edge technology and constant innovation.

• Global impact: Working at Facebook would allow me to contribute to a platform that connects billions of people worldwide.

• Opportunities for growth: Facebook offers a dynamic and fast-paced work environment with ample opp...read more
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Q2. Whats the best feature you like in Facebook?
Ans. 
I appreciate the personalized news feed feature on Facebook.
• Personalized news feed shows content based on user interests

• Helps users stay updated on relevant information

• Allows users to engage with content they are interested in
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Round duration - 90 minutes
Round difficulty - Hard

This was an online coding round where we had 2 questions to solve under 90 minutes . Both the questions were preety hard according to me . One has to have a fair share of knowledge in Data Structures and Algorithms to pass this round .

Q1. 
Longest Increasing Path in a 2D Matrix Problem Statement
Given a matrix of non-negative integers of size 'N x M', where 'N' and 'M' denote the number of rows and columns respectively, find the length of t...read more
Ans. 
The task is to find the length of the longest increasing path in a 2D matrix, where you can move in four directions: left, right, up, or down from each cell.
• Traverse the matrix and for each cell, find the longest increasing path starting from that cell

• Use dynamic programming to store the length of the longest increasing path for each cell

• Recursively explore all four directions from each cell, checking if the next cell ...read more
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Q2. 
Saving Money Problem Statement
Ninja is adventurous and loves traveling while being mindful of his expenses. Given a set of 'N' stations connected by 'M' trains, each train starting from station 'A' and r...read more
Ans. 
The task is to find the cheapest price from the given source to destination with up to K stops.
• Read the number of test cases

• For each test case, read the number of stations and trains

• Read the details of each train (source, destination, ticket price)

• Read the source station, destination station, and maximum number of stops

• Implement a graph data structure to represent the stations and trains

• Use a modified version of Dijkst...read more
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Round duration - 60 Minutes
Round difficulty - Medium

This Round was DS and Algo round and it started with formal introduction, followed by 2 problems. We first dicussed the
approach the time complexity and proper code covering all cases.

Q1. 
K - Sum Path In A Binary Tree
Given a binary tree where each node contains an integer value, and a value 'K', your task is to find all the paths in the binary tree such that the sum of the node values in ...read more
Ans. 
The task is to print every path of a binary tree with the sum of nodes in the path as 'K'.
• Traverse the binary tree and keep track of the current path and its sum

• At each node, check if the sum of the current path equals 'K'

• If yes, add the current path to the result

• Continue traversing the left and right subtrees recursively

• Remove the current node from the path before backtracking
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Q2. 
Combination Sum Problem Statement
Given an array of distinct positive integers ARR and a non-negative integer 'B', find all unique combinations in the array where the sum is equal to 'B'. Numbers can be c...read more
Ans. 
The task is to find all unique combinations in an array whose sum is equal to a given target sum.
• Use backtracking to generate all possible combinations

• Sort the array in non-decreasing order to ensure elements in each combination are in non-decreasing order

• Start with an empty combination and iterate through the array, adding each element to the combination and recursively calling the function with the remaining sum

• If th...read more
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Round duration - 50 Minutes
Round difficulty - Medium

This Round was DS/Algo + Core round and it started with formal introduction, followed by 3 problems. We first dicussed
the approach the time complexity and proper code covering all cases for the 2 coding problems . The last question was
related to OS and was a bit theoretical .

Q1. 
Merging Accounts Problem
Given a list ACCOUNTS where each element consists of a list of strings, with the first element being the name of the account holder, and the subsequent elements being the email ad...read more
Ans. 
The task is to merge accounts belonging to the same person based on common emails and return the merged accounts.
• Iterate through each account and create a mapping of emails to account holders

• Iterate through the mapping and merge accounts with common emails

• Sort the merged accounts and return the result
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Q2. 
Binary Tree Construction from Preorder and Inorder Traversal
The goal is to construct a binary tree from given preorder and inorder traversal lists of the tree nodes.
Example:
Input:
preorder = [1, 2, ...read more
Ans. 
The task is to construct a binary tree using the given inorder and preorder traversals.
• Use the preorder traversal to determine the root of the binary tree

• Use the inorder traversal to determine the left and right subtrees of the root

• Recursively construct the left and right subtrees

• Return the root node of the constructed binary tree
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Q3. Can you explain the concept of demand paging?
Ans. 
Demand paging is a memory management technique where pages are loaded into memory only when needed.
• Demand paging allows for efficient memory utilization by loading pages into memory on demand.

• It reduces the amount of initial memory required to start a process.

• When a page is needed but not in memory, a page fault occurs and the required page is loaded from disk.

• Demand paging allows for larger virtual memory space than p...read more
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Round duration - 60 minutes
Round difficulty - Medium

This was a preety intense round as I was grilled more on my System Design concepts but eventually I was able to
asnwers all the questions with some help from the interviewer.

General Tip : While preparing for Facebook Interviews , make sure you read and understand some of the most important features that Facebook incorporates like Graph Search , Adding a friend , Removing a friend , Storing Likes/Dislikes and so on. 
All these features are important to learn because at their core they are nothing but Data Structures used and implemented very elegantly . So before your next Facebook interview , do read these topics and be confident about your LLD as well as HLD skills.

Q1. How does Facebook store likes and dislikes?
Ans. 
Facebook stores likes/dislikes using a combination of databases and caching systems.
• Likes/dislikes are stored in a distributed database system like Cassandra or HBase.

• Each like/dislike is associated with a user and the content being liked/disliked.

• The database is sharded to handle the large volume of likes/dislikes.

• Caching systems like Memcached or Redis are used to improve read performance.

• Likes/dislikes can be stored...read more
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Q2. How does Facebook implement graph search?
Ans. 
Facebook implements graph search by indexing user connections and content to enable efficient search queries.
• Facebook indexes user connections and content to build a graph database.

• The graph database is used to store and retrieve information about users, their relationships, and their content.

• Graph search queries are executed by traversing the graph database to find relevant connections and content.

• Facebook uses variou...read more
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Q3. How does Facebook Chat work?
Ans. 
Facebook Chat is a real-time messaging system that allows users to send and receive instant messages.
• Facebook Chat uses a client-server architecture.

• It utilizes long polling or WebSockets for real-time communication.

• Messages are stored in a message queue for delivery.

• Chat messages are encrypted for security.

• Facebook Chat supports features like read receipts, typing indicators, and group chats.
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Q1. JS basics, promise, async await, debounce, etc.
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Round duration - 60 minutes
Round difficulty - Easy

In first round they asked me 2 coding questions where he asked me to code as close as possible to the actual one.

Q1. 
Ninja and Sorted Array Merging Problem
Ninja is tasked with merging two given sorted integer arrays ARR1 and ARR2 of sizes 'M' and 'N', respectively, such that the merged result is a single sorted array w...read more
Ans. 
Merge two sorted arrays into one sorted array in place.
• Use two pointers to compare elements from both arrays and place them in the correct position in ARR1.

• Start from the end of ARR1 and compare elements from both arrays, placing the larger element at the end of ARR1.

• Continue this process until all elements from ARR2 are merged into ARR1.
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Q2. 
Word Distance Calculation
Given a document represented as an array/list ARR of words with length N, find the smallest distance between two given words for multiple queries. The distance is defined as the ...read more
Ans. 
Find the smallest distance between two words in a document for multiple queries.
• Iterate through the document array to find the indices of the two words in each query.

• Calculate the absolute difference between the indices to get the distance.

• If a word from the query is not present in the document, return the length of the document array.

• Repeat the process for each query and output the smallest distance for each.
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Round duration - 60 minutes
Round difficulty - Easy

Then in the second round they asked a little about tree and told me to code 2 codes.

Q1. 
Level Order Traversal Problem Statement
Given a binary tree of integers, return the level order traversal of the binary tree.
Input:
The first line contains an integer 'T', representing the number of te...read more
Ans. 
The problem requires implementing a function to return the level order traversal of a binary tree.
• Implement a function that takes the root of the binary tree as input and returns the level order traversal of the tree.

• Use a queue data structure to perform level order traversal.

• Process each level of the tree one by one, starting from the root node.

• Print the node values at each level in the order they appear from left to ...read more
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Q2. 
Combination Sum Problem Statement
Given an array of distinct positive integers ARR and a non-negative integer 'B', find all unique combinations in the array where the sum is equal to 'B'. Numbers can be c...read more
Ans. 
Find all unique combinations in an array where the sum is equal to a given target sum, with elements in non-decreasing order.
• Use backtracking to generate all possible combinations.

• Sort the array to ensure elements are in non-decreasing order.

• Track the current combination and sum while backtracking.

• Terminate recursion when the sum equals the target sum.

• Avoid duplicates by skipping elements that have been used in previou
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Round duration - 30 minutes
Round difficulty - Easy

HR round with typical behavioral problems.