TikTok IOS Developer Interview Questions and Answers

Round duration - 150 Minutes
Round difficulty - Medium

3 coding questions and 20 mcq's

Q1. 
Maximum Sum of Two Non-Overlapping Subarrays
Given an integer array ARR and a positive integer K, your task is to determine two non-overlapping subarrays of length K that yield the maximum combined sum.
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Ans. 
The task is to find two non-overlapping subarrays of length K in an array, such that their sum is maximum.
• Iterate through the array and calculate the sum of each subarray of length K

• Store the maximum sum obtained from the first subarray

• Iterate again and calculate the sum of each subarray of length K, excluding the previous subarray

• Store the maximum sum obtained from the second subarray

• Return the sum of the two maximum
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Q2. 
Distinct Subsequences Problem Statement
You are given a string 'S' of length 'N' which may include duplicate alphabets. Your goal is to calculate the number of distinct subsequences in the string.
Exampl...read more
Ans. 
The task is to find the count of distinct subsequences in a given string.
• Use dynamic programming to solve the problem.

• Create a 2D array to store the count of distinct subsequences for each prefix of the string.

• Initialize the first row of the array with 1, as there is only one subsequence of an empty string.

• For each character in the string, calculate the count of distinct subsequences by considering two cases: including...read more
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Q3. 
Array Intersection Problem Statement
Given two integer arrays/ lists ARR1 and ARR2 of sizes N and M respectively, you are required to determine their intersection. An intersection is defined as the set of...read more
Ans. 
The task is to find the intersection of two integer arrays/lists.
• Read the number of test cases

• For each test case, read the size and elements of the first array/list

• Read the size and elements of the second array/list

• Find the intersection of the two arrays/lists

• Print the intersection elements in the order they appear in the first array/list
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Round duration - 120 Minutes
Round difficulty - Medium

Online video call based round, Timing was 10-11 AM
Interview started with basic greetings, post that i explained by projects in brief and then we jumped right into dsa questoins.

Q1. 
Number of Islands Problem Statement
You are given a non-empty grid that consists of only 0s and 1s. Your task is to determine the number of islands in this grid.
An island is defined as a group of 1s (re...read more
Ans. 
The task is to find the number of islands in a grid consisting of 0s and 1s.
• An island is a group of 1s connected horizontally, vertically, or diagonally

• The grid is surrounded by 0s on all four edges

• Use a depth-first search (DFS) or breadth-first search (BFS) algorithm to traverse the grid and count the number of islands

• Initialize a visited array to keep track of visited cells

• For each unvisited cell with a value of 1, p...read more
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Q2. 
Arrangement Problem Statement
Determine the number of permutations of list A = [1, 2, ..., N] such that for every index i, either A[i] is divisible by i or i is divisible by A[i].
Input:
The input start...read more
Ans. 
The goal is to find the number of permutations of a list satisfying certain conditions.
• Iterate through all permutations of the list

• Check if each permutation satisfies the given conditions

• Count the number of permutations that satisfy the conditions

• Return the count for each test case
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Q3. 
Idempotent Matrix Verification
Determine if a given N * N matrix is an idempotent matrix. A matrix is considered idempotent if it satisfies the following condition:
M * M = M
Input:
The first line cont...read more
Ans. 
An idempotent matrix is a square matrix that remains unchanged when multiplied by itself.
• Check if the given matrix satisfies the property M*M = M

• Iterate through each element of the matrix and perform the matrix multiplication

• Compare the result with the original matrix

• If they are equal, return true; otherwise, return false
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Round duration - 120 Minutes
Round difficulty - Easy

This was EM round, started with me explaining my projects in deep and facing some counter questions on that, proceeded to os, dbms basic questions and some low level designing and lastly a puzzle to end interview.

Q1. Can you design an attendance management system?
Ans. 
Design attendance management system
• Create a database to store employee information

• Implement a user interface for employees to mark their attendance

• Develop a system to track and record attendance data

• Generate reports and analytics based on attendance data
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Round duration - 20 Minutes
Round difficulty - Easy

This was formality round, HR came and explained what meesho does and told my joining dates and compensation details.

3 Moderate questions were asked. I managed to solve 2 completely and 1 partially.

Q1. Question related to system design were asked.
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Q2. He asked me to design some functions of facebook.
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Q1. Introduction type questions were asked. In this it will prefer only CS students
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There were 2 questions.
1. Knapsack
2. Median in an array

Q1. LLD(machine coding) of Google meet
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Q1. In depth discussion on my projects and resume
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2 medium - question 1 array and 1 dp
1 med to hard - dynamic programming

Q1. System design LLD - Polling System
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Q2. How to implement Concurrency in it.
Ans. 
Concurrency in software development allows multiple tasks to run simultaneously, improving performance and responsiveness.
• Use multithreading to execute multiple tasks concurrently

• Implement asynchronous programming to handle tasks that may take longer to complete

• Use synchronization techniques like locks and semaphores to manage access to shared resources

• Consider using thread pools to manage and reuse threads efficiently
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3 coding question
2 medium 1 hard

Q1. Online polling system based on OOPs
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Q2. Explaining the above code
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Q1. What is thread ?
Ans. 
A thread is a lightweight process that can run concurrently with other threads within the same process.
• Threads allow for parallel execution of tasks within a single process.

• Threads share the same memory space and resources of the process they belong to.

• Threads can communicate with each other through shared memory or message passing.

• Examples: Java threads, POSIX threads (pthreads) in C/C++.
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Q2. Inter process communication and project?
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Seat reservation system
bit manipulation
binary tree related

Q1. Bfs / dfs traversal question
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Q1. Stock buy and sell with at most 2 transaction
Ans. 
Implement a solution to find the maximum profit from buying and selling stocks with at most 2 transactions.
• Use dynamic programming to keep track of maximum profit at each day with 0, 1, or 2 transactions.

• Consider the possibility of splitting the transactions into two separate parts.

• Calculate the maximum profit by iterating through the prices array and updating the maximum profit accordingly.
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Q2. Binary search to find target
Ans. 
Binary search is a divide and conquer algorithm that efficiently finds a target value in a sorted array.
• Divide the array in half and compare the target value with the middle element

• If the target is less than the middle element, search the left half. If greater, search the right half

• Repeat the process until the target is found or the subarray is empty
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Q1. General about project
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Q2. Design paytm wallet
Ans. 
Design a digital wallet system similar to Paytm.
• Allow users to add money to their wallet using various payment methods like credit/debit cards, net banking, UPI, etc.

• Enable users to make payments for various services like mobile recharge, bill payments, online shopping, etc.

• Implement security measures like two-factor authentication, encryption of sensitive data, and regular security audits.

• Provide features like transac...read more
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