300+ Walmart Interview Questions and Answers

Find the number with the maximum frequency in an array of integers.

• Create a hashmap to store the frequency of each element in the array.

• Iterate through the array to update the frequency count.

• Find the element with the maximum frequency and return it.

• If multiple elements have the same maximum frequency, return the one with the lowest index.

Graph

• Use a graph data structure to represent people as nodes and friend relations as edges

• Each person can be represented as a node with their unique identifier

• Friend relations can be represented as directed edges between nodes

• This allows for efficient traversal and retrieval of friend connections

Given a string STR and a non-empty string PTR, find all starting indices of anagrams of PTR within STR.

• Create a frequency map of characters in PTR.

• Use sliding window technique to check anagrams in STR.

• Return the starting indices of anagrams found.

Given an integer, find the final single-digit value after summing its digits iteratively.

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

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

• Handle multiple test cases as input

Use matrix exponentiation to efficiently compute the Nth Fibonacci number modulo 10^9 + 7.

• Implement matrix exponentiation to calculate Fibonacci numbers efficiently.

• Use the formula F(n) = F(n-1) + F(n-2) with initial values F(1) = F(2) = 1.

• Return the result modulo 10^9 + 7 to handle large Fibonacci numbers.

• Optimize the solution to achieve better than O(N) time complexity.

Find the minimum number of increments needed to make all elements of the array distinct by increasing any element by 1 in each operation.

• Iterate through the array and keep track of the frequency of each element.

• For each element with frequency greater than 1, increment it until it becomes distinct.

• Return the total number of operations needed to make all elements distinct.

Implement a function to encode a text message using run-length encoding.

• Iterate through the message and count consecutive characters

• Append the character and its count to the encoded message

• Handle edge cases like single characters or empty message

Custom stack with methods to return min and max elements

• Implement a stack using an array or linked list

• Track the minimum and maximum elements using additional variables

• Update the minimum and maximum variables during push and pop operations

• Implement methods to return the minimum and maximum elements

Find the minimum cost to buy a specific weight of oranges given the cost of different weight packets.

• Iterate through the list of costs and find the minimum cost to achieve the desired weight.

• Keep track of the minimum cost for each weight up to the desired weight.

• Handle cases where a specific weight packet is unavailable by setting the cost to infinity.

• Return the minimum cost for the desired weight, or -1 if it is not possible to achieve that weight.

Return all possible non-empty subsequences with distinct characters from a given string.

• Use a recursive approach to generate all possible subsequences with distinct characters.

• Keep track of the characters used in each subsequence to ensure uniqueness.

• Return the generated subsequences as an array of strings.

Calculate the score of a string of balanced parentheses based on specific game rules.

• Iterate through the string and keep track of the score based on the rules provided

• Use a stack to keep track of the scores of valid parentheses expressions

• For each '()', increment the score by 1; for '(x)', double the score of x

• Return the final computed score for the string

Determine if two strings are similar based on given conditions.

• Check if the strings are equal first.

• Then check if the strings can be divided into two halves with similar patterns.

• Return 1 if the strings are similar, 0 otherwise.

Construct a binary tree from given POSTORDER and PREORDER traversals.

• Use the first element in PREORDER as the root node

• Find the root node in POSTORDER to divide the tree into left and right subtrees

• Recursively construct left and right subtrees using the divided traversals

The task is to find the total number of ways to make change for a specified value using given denominations.

• Use dynamic programming to solve this problem efficiently.

• Create a 2D array to store the number of ways to make change for each value using different denominations.

• Initialize the base cases and then iterate through the denominations to fill up the array.

• The final answer will be in the last cell of the array corresponding to the specified value.

Given a tree and a node, print all ancestors of Node

• Start from the given node and traverse up the tree

• While traversing, keep track of the parent nodes

• Print the parent nodes as you traverse up until reaching the root

Calculate the sum of leaf nodes at the deepest level of a binary tree.

• Traverse the binary tree to find the deepest level of leaf nodes.

• Sum the leaf nodes at the deepest level.

• Handle null nodes represented by -1.

• Ensure the sum fits within a 32-bit integer.

Design a data structure with insert, delete, search, and getRandom operations, all in constant time.

• Use a combination of HashMap and ArrayList to achieve constant time operations.

• For insert operation, add the element to the ArrayList and store its index in the HashMap.

• For delete operation, swap the element to be deleted with the last element in the ArrayList, update the index in the HashMap, and then remove the last element.

• For search operation, check if the element exists in...read more

Explanation of useState, useEffect, useMemo, and useCallback hooks in React functional components.

• useState is used to manage state in functional components

• useEffect is used for handling side effects like data fetching, subscriptions, etc.

• useMemo is used for performance optimization by memoizing expensive calculations

• useCallback is used for memoizing functions to prevent unnecessary re-renders

• These hooks enhance functional components by providing state management, side effect ...read more

House Robber problem where a robber wants to maximize stolen money without robbing adjacent houses in a circular street.

• Use dynamic programming to keep track of maximum stolen money at each house.

• Consider two cases: either rob the current house and skip the next, or skip the current house.

• Handle circular arrangement by considering the first and last houses separately.

• Example: For arr[] = {2, 3, 2}, the output is 3. Rob house 2 as it gives maximum money without triggering alar...read more

Find the maximum sum of an increasing subsequence with exactly K elements in an array of integers.

• Iterate through the array and maintain a dynamic programming table to store the maximum sum of increasing subsequences ending at each index.

• For each element, check all previous elements to find the increasing subsequence with maximum sum ending at that element.

• Update the dynamic programming table with the maximum sum found so far.

• Return the maximum sum of an increasing subsequenc...read more

Check if an array of integers consists of consecutive numbers.

• Iterate through the array and check if the absolute difference between consecutive elements is 1.

• Sort the array and check if the elements are consecutive.

• Use a set to store the elements and check if the size of the set is equal to the length of the array.

Find the maximum depth of a binary tree given its level order traversal.

• Traverse the tree level by level and keep track of the depth using a queue data structure.

• For each level, increment the depth by 1 until all nodes are processed.

• Return the maximum depth encountered during traversal as the final result.

• Example: For input [5, 10, 15, 20, -1, 25, 30, -1, 40, -1, -1, -1, -1, 45], the maximum depth is 7.

Sliding window maximum problem where we find maximum element in each window of size K.

• Use a deque to store indices of elements in decreasing order within the window.

• Pop elements from the deque that are out of the current window.

• Add the maximum element to the result for each window.

Design a Least Recently Used (LRU) cache data structure that supports get and put operations with capacity constraint.

• Implement a doubly linked list to maintain the order of keys based on their recent usage.

• Use a hashmap to store key-value pairs for quick access.

• When capacity is reached, evict the least recently used item before inserting a new item.

• Update the position of a key in the linked list whenever it is accessed or updated.

To add and manipulate elements in arrays using JavaScript, you can use array methods like splice() and slice().

• Use the splice() method to insert elements into an array at a specific index. For example, arr.splice(index, 0, 'watermelon') will insert 'watermelon' at the specified index without removing any elements.

• To manipulate elements in an array, you can use methods like splice() to remove elements or slice() to extract a portion of the array.

• Remember that arrays in JavaScr...read more

Find the Kth largest element in a given list of numbers.

• Sort the array in descending order.

• Return the Kth element from the sorted array.

• Handle multiple test cases efficiently.

Determine the minimum number of integers to be added to an array to make its sum equal to a given value.

• Iterate through the array and calculate the current sum.

• Determine the difference between the target sum and the current sum.

• Add the minimum number of integers within the range of -MAXVAL to MAXVAL to reach the target sum.

Check if a binary tree is a Complete Binary Tree or not based on given criteria.

• Traverse the binary tree level by level and check if all levels are completely filled except the last one.

• Ensure all nodes at the last level are positioned at the leftmost side.

• Use level order traversal to check for completeness of the binary tree.

• Example: For input 1 2 3 4 -1 5 6 -1 7 -1 -1 -1 -1 -1 -1, the output should be 1.

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 odd frequency, return true.

• Otherwise, return false.

Check if a given word is present in a sentence as a complete word.

• Split the sentence into words using spaces as delimiter.

• Check if the given word matches any of the words in the sentence.

• Ensure that the word is not just a substring of another word in the sentence.

Given an array of digits, find the maximum number that can be achieved by performing at most one swap.

• Iterate through the array to find the maximum digit.

• If the maximum digit is already at the beginning, find the next maximum digit and swap them.

• If the maximum digit is not at the beginning, swap it with the digit at the beginning.

The for loop will run indefinitely without any condition to terminate it.

• The loop will continue executing until it is manually interrupted or the program crashes.

• This can lead to a program becoming unresponsive or consuming excessive resources.

• It is important to always include a condition in a for loop to control its execution.

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.

• Example: For each node, ensure all nodes in its left subtree are less and all nodes in its right subtree are greater.

Given two sorted linked lists, find the intersection of elements in both lists and return a new sorted linked list.

• Traverse both linked lists simultaneously to find common elements

• Create a new linked list to store the intersecting elements

• Ensure the final linked list is sorted in ascending order

• Handle cases where there are no common elements between the lists

Identify the duplicate integer in an array of size N containing numbers between 1 and N-1.

• Iterate through the array and keep track of the frequency of each element using a hashmap.

• Return the element with a frequency greater than 1 as the duplicate integer.

• Ensure the constraints are met and a duplicate number is guaranteed to be present in the array.

Given a string, select smallest character from first K characters, remove it, and append to new string until original string is empty.

• Iterate through the string, selecting the smallest character from the first K characters each time.

• Remove the selected character from the original string and append it to the new string.

• Repeat the process until the original string is empty.

• Return the final new string formed after the operations.

Find the equilibrium index of an array where sum of elements on left equals sum on right.

• Iterate through the array and calculate prefix sum and suffix sum at each index.

• Compare prefix sum and suffix sum to find equilibrium index.

• Return the left-most equilibrium index found.

Find all paths in a binary tree where the sum of node values equals a given value 'K'.

• Traverse the binary tree using DFS and keep track of the current path and its sum.

• At each node, check if the current sum equals 'K' and add the path to the result if true.

• Continue traversal to the left and right child nodes recursively.

• Return the list of paths that sum up to 'K'.

Find the minimum cost to connect all sticks into one by joining two sticks at a time.

• Sort the array of stick lengths in non-decreasing order.

• Keep adding the two smallest sticks at a time to minimize cost.

• Repeat until all sticks are connected into one.

Design and code a scheduler for allocating meeting rooms based on input of room counts and timestamps.

• Create a table with columns for room number, start time, and end time

• Use SQL queries to check for available slots and allocate rooms

• Consider edge cases such as overlapping meetings and room availability

• Use a loop to continuously check for available slots and allocate rooms

• Implement error handling for invalid input

Code to find median of datapoints in two sorted arrays

• Use binary search to find the median index

• Divide the arrays into two halves based on the median index

• Compare the middle elements of the two halves to determine the median

Different approaches for data cleaning include removing duplicates, handling missing values, correcting inconsistent data, and standardizing formats.

• Remove duplicates

• Handle missing values

• Correct inconsistent data

• Standardize formats

• Use statistical methods to identify outliers

• Check for data accuracy and completeness

• Normalize data

• Transform data types

• Apply data validation rules

Construct a balanced binary search tree from a sorted array.

• Create a recursive function to construct the BST by selecting the middle element as the root.

• Recursively construct the left subtree with elements to the left of the middle element and the right subtree with elements to the right.

• Ensure that the constructed tree is balanced by maintaining the height difference of left and right subtrees at most 1.

Find the minimum number of jumps Bob needs to make from shop 0 to reach the final shop, or return -1 if impossible.

• Use a greedy approach to keep track of the farthest reachable shop from the current shop.

• If at any point the current shop is not reachable, return -1.

• Update the current farthest reachable shop as you iterate through the array.

Given pairs of integers, find the length of the longest pair chain where each pair follows the given condition.

• Sort the pairs based on the second element in ascending order.

• Iterate through the sorted pairs and keep track of the maximum chain length.

• Update the chain length if the current pair can be added to the chain.

• Return the maximum chain length as the result.

Recursively remove consecutive duplicates from a given string.

• Use recursion to check for consecutive duplicates in the string.

• If current character is same as next character, skip the next character.

• Repeat the process until no consecutive duplicates are found.

Find pairs of elements in an array that sum up to a given value, sorted in a specific order.

• Iterate through the array and for each element, check if the complement (S - current element) exists in a hash set.

• If the complement exists, add the pair to the result list.

• Sort the result list based on the criteria mentioned in the question.

• Return the sorted list of pairs.

Check if a given graph is bipartite by dividing its vertices into two independent sets.

• Create two sets 'U' and 'V' to store vertices based on their connections

• Use BFS or DFS to traverse the graph and assign vertices to sets

• Check if any edge connects vertices within the same set, if yes, the graph is not bipartite

Find the next smaller element for each element in an array.

• Iterate through the array from right to left and use a stack to keep track of elements.

• Pop elements from the stack until a smaller element is found or the stack is empty.

• If a smaller element is found, that is the next smaller element. If the stack is empty, there is no smaller element.

Hyperparameters of XGBoost, Random Forest, and SVM can be tuned using techniques like grid search, random search, and Bayesian optimization.

• For XGBoost, important hyperparameters to tune include learning rate, maximum depth, and number of estimators.

• For Random Forest, important hyperparameters to tune include number of trees, maximum depth, and minimum samples split.

• For SVM, important hyperparameters to tune include kernel type, regularization parameter, and gamma value.

• Grid ...read more

Microservices are implemented using RESTful APIs and message brokers for asynchronous communication.

• RESTful APIs are used for synchronous communication between microservices.

• Message brokers like Kafka or RabbitMQ are used for asynchronous communication.

• Microservices communicate with each other using HTTP requests and responses.

• Each microservice has its own database and communicates with other microservices through APIs.

• Microservices are loosely coupled and can be developed an...read more

Hyperparameters of XGBoost can be tuned using techniques like grid search, random search, and Bayesian optimization.

• Use grid search to exhaustively search through a specified parameter grid

• Utilize random search to randomly sample hyperparameters from a specified distribution

• Apply Bayesian optimization to sequentially choose hyperparameters based on the outcomes of previous iterations

The task is to determine and return the top view of a given Binary Tree of integers.

• The top view of a binary tree consists of all the nodes visible when the tree is viewed from the top.

• Identify the nodes that appear on the top when looking from above the tree.

• Output the top view as a space-separated list of node values from left to right.

Static polymorphism is achieved at compile time through method overloading and overriding. Dynamic polymorphism is achieved at runtime through method overriding.

• Static polymorphism is also known as compile-time polymorphism.

• Dynamic polymorphism is also known as runtime polymorphism.

• Static polymorphism is achieved through method overloading, where multiple methods have the same name but different parameters.

• Dynamic polymorphism is achieved through method overriding, where a su...read more

Setting up Redux store, connecting components, managing actions and reducers, and using middleware like Redux Thunk or Redux Saga for handling asynchronous actions.

• Setting up a Redux store involves creating a store with createStore() function from Redux, combining reducers with combineReducers(), and applying middleware like Redux Thunk or Redux Saga.

• Connecting components to the Redux store can be done using the connect() function from react-redux library, which allows compon...read more

The problem is to color a graph with two colors such that no two connected vertices have the same color.

• Use a graph coloring algorithm such as Depth First Search (DFS) or Breadth First Search (BFS).

• Start with an arbitrary vertex and color it with one color (e.g., blue).

• Color all its adjacent vertices with the other color (e.g., red).

• Continue this process for all connected components of the graph.

• If at any point, you encounter two adjacent vertices with the same color, it is n...read more

Hyperparameters are settings that control the behavior of machine learning algorithms.

• Hyperparameters are set before training the model.

• They control the learning process and affect the model's performance.

• Examples include learning rate, regularization strength, and number of hidden layers.

• Optimizing hyperparameters is important for achieving better model accuracy.

A program to simulate a race with 5 people using multithreading and determine the winner.

• Create a class for the race participants

• Implement the Runnable interface for each participant

• Use a thread pool to manage the threads

• Start all threads simultaneously

• Wait for all threads to finish

• Determine the winner based on the finishing time

Java is platform-independent because the code is compiled into bytecode that can run on any platform with a JVM, which is platform-dependent due to its reliance on the underlying hardware and operating system.

• Java code is compiled into bytecode, which can run on any platform with a JVM.

• JVM acts as an interpreter that translates bytecode into machine code specific to the underlying hardware and operating system.

• The JVM provides a layer of abstraction between the Java code and ...read more

An unique id for a massive parallel system can be generated using a combination of timestamp, machine id and a random number.

• Use a timestamp to ensure uniqueness

• Include a machine id to avoid collisions in a distributed system

• Add a random number to further increase uniqueness

• Consider using a UUID (Universally Unique Identifier) for simplicity

• Ensure the id generation algorithm is thread-safe

I follow the MVC design pattern as it separates concerns and promotes code reusability.

• MVC separates the application into Model, View, and Controller components.

• Model represents the data and business logic.

• View represents the user interface.

• Controller handles user input and updates the model and view accordingly.

• MVC promotes code reusability and maintainability.

• Example: Ruby on Rails framework follows MVC pattern.

Data is collected from various sources including databases, APIs, and user input.

• We have access to multiple databases where we can extract relevant data

• We use APIs to gather data from external sources such as social media platforms

• Users can input data through forms or surveys

• We also collect data through web scraping techniques

The sequence of execution of SQL codes is Select-From-Where-Group By-Having-Order By.

• Select: choose the columns to display

• From: specify the table(s) to retrieve data from

• Where: filter the data based on conditions

• Group By: group the data based on a column

• Having: filter the grouped data based on conditions

• Order By: sort the data based on a column

Code to describe database and columns from a table

• Use SQL SELECT statement to retrieve column names and data types

• Use DESC command to get table structure

• Use INFORMATION_SCHEMA.COLUMNS to get detailed information about columns

• Use SHOW CREATE TABLE to get table creation statement

Hyperparameters in XGBoost algorithm control the behavior of the model during training.

• Hyperparameters include parameters like learning rate, max depth, number of trees, etc.

• They are set before the training process and can greatly impact the model's performance.

• Example: 'learning_rate': 0.1, 'max_depth': 5, 'n_estimators': 100

Ridge and LASSO regression are both regularization techniques used in linear regression to prevent overfitting by adding penalty terms to the cost function.

• Ridge regression adds a penalty term equivalent to the square of the magnitude of coefficients (L2 regularization).

• LASSO regression adds a penalty term equivalent to the absolute value of the magnitude of coefficients (L1 regularization).

• Ridge regression tends to shrink the coefficients towards zero but does not set them e...read more

The Josephus Problem involves eliminating every Kth person in a circle of N individuals until only one person remains. Determine the position of the last person standing.

• Use a circular linked list to simulate the elimination process efficiently

• Implement a function to find the position of the last person standing based on the given N and K values

• Consider edge cases such as when N=1 or K=1

• Optimize the solution to handle large values of N and K efficiently

Excel functions are pre-built formulas that perform calculations or manipulate data in a spreadsheet.

• Sum: adds up a range of numbers

• Sum if: adds up a range of numbers based on a specified condition

• Count: counts the number of cells in a range that contain numbers

• CountA: counts the number of cells in a range that are not empty

• Count Blanks: counts the number of empty cells in a range

Steps to fit a time series model

• Identify the time series pattern

• Choose a suitable model

• Split data into training and testing sets

• Fit the model to the training data

• Evaluate model performance on testing data

• Refine the model if necessary

• Forecast future values using the model

Use two wires of different lengths to measure a specific amount of time by burning them simultaneously.

• Burn both wires at the same time, one wire will burn faster than the other.

• Measure the time it takes for the faster burning wire to completely burn.

• Calculate the specific amount of time by using the ratio of the lengths of the two wires.

The ants will end up at the center of the triangle.

• The ants will move towards each other in a straight line.

• They will meet at the centroid of the triangle, which is the point where all three medians intersect.

• The centroid is located at two-thirds of the distance from each vertex to the midpoint of the opposite side.

Mocking components in Jest for testing with props and named exports

• Use jest.mock() to mock components and their exports

• For handling props, use jest.fn() to create mock functions and pass them as props to the component being tested

• For named exports, use jest.mock() with a second argument to specify the module's exports

Design a Java-like Garbage Collector with minimal configurations.

• Choose a garbage collection algorithm (e.g. mark-and-sweep, copying, generational)

• Determine the heap size and divide it into regions (e.g. young, old, permanent)

• Implement a root set to keep track of live objects

• Set thresholds for garbage collection (e.g. occupancy, time)

• Implement the garbage collection algorithm and test for memory leaks

We implement multiple checks and balances to ensure payments are credited to the correct employee account.

• We verify the employee's account number and name before processing any payment.

• We implement a two-step verification process to ensure accuracy.

• We conduct regular audits to ensure all payments are correctly credited.

• We have a dedicated team to handle any payment discrepancies or errors.

• We provide training to employees on how to verify and confirm payment details.

• We use adv...read more

CSV files are plain text files that store tabular data, while Excel files are binary files that can contain multiple sheets and complex formatting.

• CSV files are simpler and more lightweight compared to Excel files.

• CSV files can be easily opened and edited using a text editor, while Excel files require specific software like Microsoft Excel.

• CSV files do not support formulas, macros, or formatting options like colors and fonts, while Excel files do.

• CSV files have a smaller file...read more

I have handled large amounts of data in my previous roles.

• I have experience handling terabytes of data in my previous role as a data analyst at XYZ company.

• I have worked with data from various sources such as databases, spreadsheets, and APIs.

• I have also used tools like SQL, Python, and Excel to manipulate and analyze data.

• I am comfortable working with both structured and unstructured data.

• I have experience cleaning and transforming data to make it usable for analysis.

I would use a hash table for efficient searching of a lot of data.

• Hash tables provide constant time complexity for search operations.

• They use a hash function to map keys to array indices, allowing for quick retrieval of data.

• Examples of hash table implementations include dictionaries in Python and HashMaps in Java.

AWR report analysis is a tool used to diagnose and troubleshoot performance issues in Oracle databases.

• AWR (Automatic Workload Repository) collects and maintains performance statistics for Oracle databases.

• AWR reports provide detailed information on database performance over a period of time.

• Analysis of AWR reports helps identify performance bottlenecks, resource usage, and potential areas for optimization.

• AWR report analysis can be used in performance testing to compare data...read more

Probability of raining given 3 friends with 2/3 truth probability saying it's raining.

• Use Bayes' theorem to calculate the probability

• P(Raining | All Friends Saying It's Raining) = P(All Friends Saying It's Raining | Raining) * P(Raining) / P(All Friends Saying It's Raining)

• P(All Friends Saying It's Raining | Raining) = 1

• P(Raining) = Prior probability of raining

• P(All Friends Saying It's Raining) = Probability of all friends saying it's raining

HAVING is used with GROUP BY to filter the results after grouping. WHERE is used to filter the results before grouping.

• HAVING is used with GROUP BY clause while WHERE is used with SELECT clause.

• HAVING is used to filter the results of aggregate functions while WHERE is used to filter individual rows.

• HAVING is used to filter the results after grouping while WHERE is used to filter the results before grouping.

• HAVING can only be used with aggregate functions while WHERE can be us...read more

Memoization is a technique used in programming to store the results of expensive function calls and return the cached result when the same inputs occur again.

• Memoization helps improve the performance of a function by caching its results.

• It is commonly used in dynamic programming to optimize recursive algorithms.

• Example: Memoizing a Fibonacci function to avoid redundant calculations.

Query to find the top five employee salaries

• Use the SELECT statement to retrieve the employee salaries

• Order the results in descending order using the ORDER BY clause

• Limit the results to the top five using the LIMIT clause

Outlier values are data points that significantly differ from the rest of the data, potentially affecting the analysis.

• Outliers can be identified using statistical methods like Z-score or IQR.

• Treatment options include removing outliers, transforming the data, or using robust statistical methods.

• Example: In a dataset of salaries, a value much higher or lower than the rest may be considered an outlier.

Stored procedures are precompiled SQL statements that can be reused and executed multiple times.

• Stored procedures improve performance by reducing network traffic and improving security.

• They can be used to encapsulate business logic and provide a consistent interface to the database.

• Stored procedures can also be used to simplify complex queries and transactions.

• Examples include procedures for inserting, updating, and deleting data, as well as generating reports and performing ...read more

Request flows in Spring Boot MVC, ways to instantiate a bean, and handling Java out-of-memory exception.

• Request flows in Spring Boot MVC: DispatcherServlet receives HTTP request, HandlerMapping maps request to appropriate controller, Controller processes request and returns response.

• Ways to instantiate a bean: Constructor injection, setter injection, and using the @Bean annotation.

• Handling Java out-of-memory exception: Analyze memory usage, increase heap size, optimize code, ...read more

Views in a database management system provide security, simplify complex queries, and improve performance.

• Enhance security by restricting access to certain columns or rows

• Simplify complex queries by pre-defining joins and aggregations

• Improve performance by storing frequently used queries as views

• Allow for data abstraction and reduce redundancy

• Provide a layer of abstraction for users to interact with the data

Instagram uses a notification system to alert users when they are tagged and displays reels on the profile page based on user preferences and algorithms.

• Instagram uses a push notification system to alert users when they are tagged in a post or story.

• Reels are displayed on the profile page based on user engagement, preferences, and algorithms.

• The Explore page also suggests reels to users based on their interests and interactions on the platform.

Use multiple threads to print numbers from 1 to 100 in an optimized approach.

• Divide the range of numbers (1-100) among the threads to avoid overlap.

• Use synchronization mechanisms like mutex or semaphore to ensure proper order of printing.

• Implement a logic where each thread prints its assigned numbers in sequence.

• Consider using a thread pool to manage and optimize thread creation and execution.

• Example: Thread 1 prints numbers 1-25, Thread 2 prints numbers 26-50, and so on.

Math.floor() is a method in JavaScript that rounds a number down to the nearest integer.

• Math.floor() returns the largest integer less than or equal to a given number.

• It is commonly used to convert a floating-point number to an integer.

• Example: Math.floor(3.9) returns 3.

A 5cm wooden cube is cut into smaller 1cm cubes. Determine the number of cubes with different numbers of painted sides.

• The original cube has 125 smaller cubes (5x5x5)

• Each smaller cube has 6 faces, so there are 750 faces in total

• The cubes on the edges have 3 painted sides, the ones on the corners have 3 painted sides, and the rest have 2 painted sides

• There are 8 cubes on the corners, 12 on the edges, and 105 in the middle

• There are 8 cubes with 3 painted sides, 36 with 2 painte...read more

A Promise is an object representing the eventual completion or failure of an asynchronous operation.

• A Promise is used to handle asynchronous operations in JavaScript.

• It represents a value that may be available now, or in the future.

• A polyfill for Promise can be implemented using the setTimeout function to simulate asynchronous behavior.

The interviewee was asked about word break, string to integer, and system design for an e-commerce app.

• Word break: Given a string and a dictionary of words, determine if the string can be segmented into a space-separated sequence of dictionary words.

• String to integer: Convert a string to an integer. Handle negative numbers and invalid inputs.

• System design e-commerce app: Design an e-commerce app with features like product listing, search, cart, checkout, payment, and order tr...read more

Reverse a linked list

• Iterate through the linked list and change the direction of the pointers

• Use three pointers to keep track of the previous, current, and next nodes

• Recursively reverse the linked list

Oracle Data Guard is a high availability and disaster recovery solution for Oracle databases.

• Oracle Data Guard consists of a primary database and one or more standby databases.

• Redo data from the primary database is transmitted to the standby database(s) to keep them synchronized.

• In case of a failure at the primary database, one of the standby databases can be activated to take over.

• Data Guard can operate in synchronous or asynchronous mode depending on the level of protection...read more

Static, final, and abstract are keywords in Java used for different purposes.

• Static is used to create variables and methods that belong to the class rather than an instance of the class.

• Final is used to declare constants or to prevent a class, method, or variable from being overridden or modified.

• Abstract is used to create abstract classes and methods that cannot be instantiated and must be implemented by subclasses.

Data abstraction is the process of hiding implementation details and showing only the necessary features of an object.

• Data abstraction can be achieved through abstract classes and interfaces in object-oriented programming.

• It helps in reducing complexity by providing a simplified view of the data.

• By using access specifiers like private, protected, and public, we can control the visibility of data members and methods.

• Example: In a car object, we can abstract the details of the ...read more

Ridge and LASSO are regularization techniques used in linear regression to prevent overfitting.

• Ridge adds a penalty term to the sum of squared errors, which shrinks the coefficients towards zero but doesn't set them exactly to zero.

• LASSO adds a penalty term to the absolute value of the coefficients, which can set some of them exactly to zero.

• The geometric interpretation of Ridge is that it adds a constraint to the size of the coefficients, which shrinks them towards the origi...read more

Arrow functions do not have their own 'this' value, which is required in constructors.

• Arrow functions do not have a 'this' binding, so 'this' will refer to the parent scope.

• Constructors require 'this' to refer to the newly created object.

• Using arrow functions in constructors can lead to unexpected behavior and errors.

DSA questions on array and binary tree manipulation

• For printing pairs with target sum, use a hash table to store frequency of elements and check if complement exists

• For converting array to BST, use binary search to find the middle element and recursively build left and right subtrees

• For top view of binary tree, use a queue to traverse the tree level by level and store horizontal distance of nodes

• For minimum number of jumps, use dynamic programming to find minimum jumps requir...read more