70+ LinkedIn Interview Questions and Answers

Construct a BST with minimum search cost based on keys and frequencies.

• Create a recursive function to construct the BST by considering all possible root nodes.

• Calculate the cost for each possible BST and return the minimum total cost.

• Optimize the solution by using dynamic programming to store intermediate results.

• Ensure that the keys are sorted and frequencies are provided for each key.

• Example: For keys [1, 3, 5] and frequencies [3, 10, 7], the minimum total cost is 30.

Calculate the total number of 'good triplets' in two arrays based on given conditions.

• Iterate through all possible triplets in both arrays and check if they satisfy the conditions

• Use nested loops to iterate through all combinations of indices in both arrays

• Check the conditions for Type 1 and Type 2 'good triplets' separately

• Increment a counter for each valid 'good triplet' found

• Return the total count of 'good triplets' for each test case

Given a string, determine if it can be split into three non-empty substrings where one is a substring of the other two.

• Check if any substring of the string is a substring of the other two substrings.

• Iterate through all possible divisions of the string into three non-empty substrings.

• Use two pointers to find all possible substrings efficiently.

Generate a number based on majority set bits in given integers array.

• Iterate through each bit position and count set and unset bits

• Construct the resulting number based on majority set bits at each position

• Return the final constructed number

Count the number of triangles in a directed and undirected graph.

• Parse the input to extract vertices, edges, and edges between vertices.

• Implement a function to count triangles in both directed and undirected graphs.

• Return the counts of triangles for each test case.

Calculate the distance between two nodes in a binary tree.

• Traverse the tree to find the paths from the root to each node

• Find the lowest common ancestor of the two nodes

• Calculate the distance by adding the distances from each node to the common ancestor

Check if two binary trees are mirrors of each other based on specific criteria.

• Compare the roots of both trees.

• Check if the left subtree of the first tree is the mirror of the right subtree of the second tree.

• Verify if the right subtree of the first tree is the mirror of the left subtree of the second tree.

The goal is to determine the maximum profit that can be achieved by buying and selling stocks on different days.

• Iterate through the stock prices and buy on days when the price is lower than the next day, and sell on days when the price is higher than the next day.

• Calculate the profit by summing up the differences between buying and selling prices.

• Repeat the process for each test case and output the maximum profit possible for each case.

DFS traversal to find connected components in an undirected and disconnected graph.

• Use Depth First Search (DFS) to traverse the graph and find connected components

• Maintain a visited array to keep track of visited vertices

• For each unvisited vertex, perform DFS to explore the connected component it belongs to

• Print the vertices of each connected component in ascending order

Find the median of two sorted arrays after merging them.

• Merge the two sorted arrays into one sorted array.

• Calculate the median based on the length of the combined array.

• Handle cases where the total number of elements is even or odd.

Count the number of distinct substrings in a given string.

• Iterate through all possible substrings and store them in a set to avoid duplicates.

• Use nested loops to generate all substrings efficiently.

• Consider using a hash set to store unique substrings.

• Example: For input 'abcd', generate substrings 'a', 'ab', 'abc', 'abcd', 'b', 'bc', 'bcd', 'c', 'cd', 'd'.

Find the minimum number of dice throws required to reach the last cell on a 'Snake and Ladder' board.

• Use Breadth First Search (BFS) to find the shortest path from the starting cell to the last cell.

• Maintain a queue to explore all possible moves from each cell.

• Consider the effect of snakes and ladders on the movement of the player.

• Handle the case where the last cell is unreachable by returning -1.

• Optimize the solution by using a visited array to avoid revisiting cells.

Convert a number to binary, take its complement, and convert back to decimal.

• Convert the given number to binary representation

• Take the complement of the binary number by swapping '1's and '0's

• Convert the complement back to decimal representation

• Return the complement number for each test case

Given an integer, sum its digits until a single-digit number is obtained.

• Iteratively sum the digits of the integer until a single-digit number is reached

• Output the final single-digit integer for each test case

• Handle multiple test cases efficiently

Identify the repeating and missing number in an array of first N positive integers.

• Iterate through the array and keep track of the sum of elements and sum of squares to find the missing and repeating numbers.

• Use a set to identify the repeating number and calculate the missing number using the sum formula.

• Handle multiple test cases by looping through each case and applying the same logic.

• Example: For nums = [1, 2, 3, 4, 4, 5], the repeating number is 4 and the missing number i...read more

The problem involves finding the number of distinct ways to climb to the Nth stair by taking one or two steps at a time.

• Use dynamic programming to solve the problem efficiently.

• The number of ways to reach the Nth stair is the sum of the number of ways to reach the (N-1)th stair and the (N-2)th stair.

• Handle base cases for N=0 and N=1 separately.

• Consider using modulo 10^9+7 to avoid overflow in calculations.

The problem involves finding the optimal strategy to accumulate the maximum amount in a coin game with specific rules.

• Start by understanding the rules of the game and how players take turns to choose coins.

• Consider the scenario where both players play optimally to maximize winnings.

• Iterate through different strategies to determine the best approach for selecting coins.

• Keep track of the total winnings accumulated by each player and choose coins accordingly.

• The output should be...read more

Validate if a given binary tree is a Binary Search Tree (BST) or not.

• Check if the left subtree of a node contains only nodes with data less than the node's data.

• Check if the right subtree of a node contains only nodes with data greater than the node's data.

• Recursively check if both the left and right subtrees are also binary search trees.

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.

Find and print all distinct palindromic substrings in a given string.

• Iterate through all possible substrings of the input string.

• Check if each substring is a palindrome.

• Store distinct palindromic substrings in a set to avoid duplicates.

• Sort the set of palindromic substrings and print them space-separated.

The task is to determine the number of ways to decode a given number string using a specific encoding.

• Use dynamic programming to solve the problem efficiently.

• Consider different cases like single digit decoding, double digit decoding, and invalid cases.

• Handle edge cases like leading zeros and empty string inputs.

• Implement a recursive function with memoization to avoid redundant calculations.

Count the number of islands in a grid of 0s and 1s connected horizontally, vertically, or diagonally.

• Iterate through the grid and perform depth-first search (DFS) to mark visited land cells as water.

• Increment the island count each time a new island is encountered during DFS.

• Consider all adjacent cells (horizontally, vertically, and diagonally) while exploring the island.

• Ensure to handle boundary conditions and check for valid land cells during DFS.

• Return the total count of is...read more

Find the length of the longest palindromic subsequence in a given string of lowercase English letters.

• Use dynamic programming to solve this problem efficiently.

• Create a 2D array to store the lengths of palindromic subsequences for different substrings.

• Fill the array diagonally based on the characters in the string.

• Return the length of the longest palindromic subsequence for each test case.

Implement a stack with push, pop, top, isEmpty, and getMin operations in O(1) time complexity without using extra space for storing additional stack data structures.

• Use two stacks - one to store the actual elements and another to store the minimum element at each level of the main stack.

• When pushing an element, compare it with the current minimum and update the minimum stack accordingly.

• For getMin operation, simply return the top element of the minimum stack.

• Ensure all operat...read more

Generate all possible valid parentheses configurations using N pairs.

• Use backtracking to generate all possible combinations of parentheses.

• Keep track of the number of open and close parentheses used.

• Add '(' if there are remaining open parentheses, and add ')' if there are remaining close parentheses.

• Base case: when the length of the generated string is 2*N, add it to the result array.

Convert a Binary Tree into a Doubly Linked List following Inorder Traversal.

• Perform Inorder Traversal of the Binary Tree to get the nodes in order.

• Create a Doubly Linked List by linking the nodes in the order obtained from Inorder Traversal.

• Return the head of the Doubly Linked List as the output.

Implement serialization and deserialization methods for a binary tree of integers.

• Use any algorithm for serialization and deserialization.

• Ensure the serialized string can be correctly decoded back to form the original binary tree.

• Nodes are separated by spaces, and -1 is used to depict a null node.

• Output the level order traversal of the deserialized binary tree with nodes separated by single spaces.

Determine if a string C is formed by interleaving two strings A and B.

• Check if the length of C is equal to the sum of lengths of A and B.

• Ensure all characters of A and B are present in C.

• Verify that the order of characters in C matches the order in A and B.

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.

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 right.

• Handle null nodes represented by -1 in the input.

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 previous combinations.

Check if a permutation of a string can form a palindrome.

• Create a frequency map of characters in the string.

• Count the number of characters with odd frequencies.

• If there is at most one character with an odd frequency, return true.

• Otherwise, return false.

TOP and PS are commands used in Unix-like operating systems to display information about running processes. TOP is called TOP because it shows the top processes consuming system resources.

• TOP is an interactive command that continuously updates the process list, while PS displays a snapshot of the current processes.

• TOP provides real-time information about CPU usage, memory usage, and other system statistics, while PS provides a static view of the processes.

• TOP allows users to ...read more

Kill all processes using JAVA with one liner command.

• Use the 'pkill' command with the '-f' option to match the process name

• Combine it with the 'pgrep' command to get the process IDs of JAVA processes

• Use a loop to kill each process by its ID

Solution to performing operations on a large array of bits.

• Use bitwise operators to perform operations on individual bits

• Use a loop to iterate through the array and perform the operations

• Ensure that the array is large enough to accommodate all the bits

• Consider using a data structure like a bitset for efficient bit manipulation

XSS attacks involve injecting malicious scripts into web pages, while SQLi attacks involve manipulating database queries. Prevention includes input validation and parameterized queries.

• XSS attacks involve injecting malicious scripts into web pages to steal data or perform actions on behalf of the user

• Prevention methods for XSS attacks include input validation, output encoding, and using Content Security Policy (CSP)

• SQLi attacks involve manipulating database queries to access ...read more

OOP allows for code reusability, modularity, and easier maintenance.

• Encapsulation: Bundling data and methods together to protect data from outside interference.

• Inheritance: Allows for the creation of new classes based on existing classes, promoting code reuse.

• Polymorphism: Objects can be treated as instances of their parent class, allowing for flexibility and extensibility.

• Modularity: Breaking down a program into smaller, manageable parts, making it easier to maintain and upd...read more

ps displays a snapshot of current processes, while top provides real-time information and allows for interactive management.

• ps displays a static list of processes, while top continuously updates the list

• top allows for interactive management of processes (e.g. killing, renicing), while ps does not

• ps is useful for a quick snapshot of processes, while top is useful for monitoring real-time system activity

The command to kill all running Java processes is 'pkill -f java'

• Use the 'pkill' command followed by the '-f' flag and 'java' keyword to kill all Java processes

• Be cautious when using this command as it will terminate all running Java processes

• Make sure to have the necessary permissions to kill processes on the system

I am familiar with testing frameworks such as JUnit, Selenium, and TestNG.

• JUnit

• Selenium

• TestNG

JSON is a lightweight data interchange format used to store and transmit data in a readable format.

• JSON uses key-value pairs to represent data.

• It is language-independent and easy to understand.

• JSON data types include strings, numbers, booleans, arrays, and objects.

• Example: {"name": "John", "age": 25}

• JSON can be used with various programming languages and APIs.

JSON is a lightweight data interchange format that is easy for humans to read and write and easy for machines to parse and generate.

• JSON is based on key-value pairs, where keys are always strings enclosed in double quotes.

• Data is organized in a hierarchical structure using objects and arrays.

• Example: {"name": "John", "age": 30}

• Example: [{"name": "Alice", "age": 25}, {"name": "Bob", "age": 35}]

Yes, there are several software testing frameworks available.

• Software testing frameworks provide a structured approach to testing software applications.

• They offer a set of guidelines, tools, and libraries to automate and streamline the testing process.

• Some popular software testing frameworks include Selenium, JUnit, TestNG, and Cucumber.

• Selenium is widely used for web application testing, while JUnit and TestNG are commonly used for unit testing in Java.

• Cucumber is a behavior...read more

The best protocol for storing images is JPEG (Joint Photographic Experts Group).

• JPEG is a widely used format for storing images due to its high compression ratio and good image quality.

• It supports millions of colors and is compatible with most devices and software.

• Other options include PNG (Portable Network Graphics) for lossless compression and GIF (Graphics Interchange Format) for animations.

The best protocol to store images is JPEG.

• JPEG is a widely used image compression format.

• It provides a good balance between image quality and file size.

• JPEG supports millions of colors and is suitable for photographs and complex images.

• Other protocols like PNG and GIF have their own advantages but may not be as efficient for storing images.

Mud logging involves monitoring drilling parameters to analyze rock formations. Viscosity, density, porosity, and permeability are key properties in drilling and geology.

• Mud logging involves analyzing drilling cuttings and fluids to determine rock properties and detect hydrocarbons.

• Viscosity refers to a fluid's resistance to flow, important for maintaining drilling mud circulation.

• Density is the mass per unit volume of a substance, crucial for balancing well pressure.

• Porosity...read more

Design a system for a traffic enforcement camera.

• 1. Install cameras at strategic locations to monitor traffic violations.

• 2. Use image recognition software to detect violations such as speeding or running red lights.

• 3. Store captured images and violation data in a secure database.

• 4. Generate automated tickets and send them to violators.

• 5. Implement a user interface for law enforcement to review violations and approve tickets.

The number of ways to parenthesize a boolean expression to evaluate to true can be found using dynamic programming.

• Use dynamic programming to count the number of ways to parenthesize the expression.

• Consider all possible ways to split the expression into subexpressions.

• Keep track of the number of ways each subexpression can evaluate to true.

• Combine the results of subexpressions to get the total number of ways to parenthesize the expression to true.

Prevent SQL injection by using parameterized queries, input validation, and escaping user input.

• Use parameterized queries to separate SQL code from user input.

• Validate and sanitize user input to prevent malicious code injection.

• Escape special characters in user input before executing SQL queries.

Using a map-based design to check for isomorphic words in a file.

• Create a map where the key is the sorted characters of a word and the value is a list of words with the same sorted characters.

• Iterate through the file, for each word, sort its characters and check if it exists in the map. If it does, add the word to the list. If not, create a new entry in the map.

• After processing the file, iterate through the map and output the lists of isomorphic words.

Automated testing involves using software tools to execute tests, while manual testing is performed by humans.

• Automated testing is faster and more efficient than manual testing.

• Automated testing can be used to perform repetitive tasks and regression testing.

• Manual testing allows for exploratory testing and human judgment.

• Automated testing requires initial setup and maintenance of test scripts.

• Both types of testing have their own advantages and disadvantages.

Checked exceptions are checked at compile time while unchecked exceptions are not checked at compile time.

• Checked exceptions are subclasses of Exception class except RuntimeException and its subclasses.

• Unchecked exceptions are subclasses of RuntimeException and Error classes.

• Checked exceptions must be caught or declared in the method signature using 'throws' keyword.

• Unchecked exceptions do not need to be caught or declared.

• Examples of checked exceptions include IOException, C...read more

Cross-site scripting (XSS) is a type of security vulnerability that allows attackers to inject malicious scripts into web pages viewed by other users.

• XSS occurs when a web application allows users to input unvalidated data that is then displayed on the page without proper encoding.

• There are three main types of XSS: stored XSS, reflected XSS, and DOM-based XSS.

• An example of XSS is when a user inputs a script into a search bar, and the script is executed when another user views...read more

To find the minimum difference between any two integers of 2 sorted lists, iterate through both lists simultaneously and keep track of the minimum difference.

• Iterate through both sorted lists simultaneously

• Keep track of the minimum difference found so far

• Update the minimum difference if a smaller difference is found

Improving production and quality requires a focus on process optimization, employee training, and continuous improvement initiatives.

• Implement lean manufacturing principles to streamline processes and reduce waste

• Invest in employee training and development to improve skills and knowledge

• Establish quality control measures and regularly monitor performance

• Encourage employee feedback and suggestions for improvement

• Regularly review and update production processes to ensure effici...read more

Perform right rotation on each node of a binary tree.

• Start from the root node and perform right rotation on each node in a recursive manner.

• Update the parent-child relationships accordingly after each rotation.

• Ensure that the binary tree structure is maintained throughout the process.

Trust and safety refers to the measures taken to ensure the safety and security of users on a platform or service.

• It involves implementing policies and procedures to prevent harmful behavior such as fraud, harassment, and hate speech.

• Trust and safety also includes measures to protect user data and privacy.

• Examples of trust and safety measures include account verification, content moderation, and user reporting systems.

• Trust and safety specialists work to maintain a safe and t...read more

ACID stands for Atomicity, Consistency, Isolation, and Durability in databases.

• Atomicity ensures that all operations in a transaction are completed successfully or none at all.

• Consistency ensures that the database remains in a consistent state before and after the transaction.

• Isolation ensures that multiple transactions can be executed concurrently without affecting each other.

• Durability ensures that once a transaction is committed, it will persist even in the event of system...read more

Risk management is the process of identifying, assessing, and prioritizing potential risks and taking measures to minimize or mitigate them.

• Identifying potential risks

• Assessing the likelihood and impact of each risk

• Prioritizing risks based on their severity

• Developing strategies to minimize or mitigate risks

• Monitoring and reviewing risks regularly

• Examples include financial risk management, cybersecurity risk management, and health and safety risk management

My sales philosophy is centered around building strong relationships, providing value, and always putting the client's needs first.

• Focus on building trust and rapport with clients

• Understand the client's needs and provide tailored solutions

• Always prioritize the client's best interests

• Consistently follow up and provide excellent customer service

• Strive to exceed client expectations

Sort a stack using another stack

• Create an empty temporary stack

• Pop elements from the original stack and push them onto the temporary stack in sorted order

• Pop elements from the temporary stack back to the original stack

Leaves of a tree are the nodes with no children in a tree data structure.

• Traverse the tree and identify nodes with no children.

• Use depth-first search or breadth-first search algorithms to find leaves.

• Examples: In a binary tree, leaves are nodes with no left or right child.

• In a general tree, leaves are nodes with no children in their child list.

The Windows function in SQL is used to perform calculations on a specific subset of rows in a result set.

• The Windows function is used with the OVER clause to define the subset of rows to perform calculations on.

• Common Windows functions include ROW_NUMBER, RANK, DENSE_RANK, and NTILE.

• Example: SELECT ROW_NUMBER() OVER (PARTITION BY department ORDER BY salary DESC) AS row_num FROM employees;

Competitive coding can be tough but with practice and dedication, it can be mastered.

• Practice regularly to improve problem-solving skills

• Understand different data structures and algorithms

• Participate in coding competitions to test and improve skills

The Lowest Common Ancestor (LCA) of a tree is the shared ancestor of two nodes farthest from the root.

• Start from the root and traverse the tree to find the paths from the root to the two nodes.

• Compare the paths to find the last common node between them, which is the LCA.

• If one of the nodes is an ancestor of the other, then the ancestor node is the LCA.

Design a monitoring system for SiteOps

• Identify key metrics to monitor such as server uptime, response time, and error rates

• Implement monitoring tools like Nagios, Zabbix, or Prometheus to track these metrics

• Set up alerts for critical thresholds to notify the team in case of issues

• Create dashboards to visualize the data and trends for easy monitoring

• Regularly review and update the monitoring system to ensure it remains effective

Automation in SiteOps involves using tools and scripts to streamline processes and reduce manual tasks.

• Automated deployment scripts for deploying code changes to servers

• Monitoring tools that automatically alert when server resources are low

• Automated backup processes for data protection

• Scheduled tasks for routine maintenance like database cleanup