40+ SDE Interview Questions and Answers for Freshers

The problem involves dividing an array into K subsets with equal sum.

• Use backtracking to try all possible combinations of subsets.

• Keep track of the sum of elements in each subset and check if they are equal to the target sum.

• Optimize by sorting the array in descending order and assigning elements to subsets greedily.

• Handle edge cases like when the sum of elements is not divisible by K.

Sort a doubly linked list where each node's position deviates at most K positions from its position in the sorted list.

• Iterate through the doubly linked list and maintain a min-heap of size K+1 to keep track of the next smallest element.

• Remove the smallest element from the heap and add it to the sorted list. Update the heap with the next element from the removed node's next position.

• Continue this process until all nodes are added to the sorted list.

Given start and end times of meetings, find the maximum number of meetings that can be scheduled in a single room.

• Sort the meetings based on their end times in ascending order.

• Iterate through the sorted meetings and select the ones that do not overlap with the previously selected meetings.

• Keep track of the selected meetings and return their indices.

Find root values of duplicate subtrees in a binary tree.

• Traverse the tree in a bottom-up manner to identify duplicate subtrees.

• Use a hashmap to store the subtree structures and their frequencies.

• Return the root values of duplicate subtrees based on hashmap entries.

A thread is a unit of execution within a process that can run independently and concurrently with other threads.

• Threads allow for concurrent execution of tasks within a program.

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

• Threads can communicate and synchronize with each other through shared data structures like locks and semaphores.

• Threads can improve performance by utilizing multiple CPU cores or by handling I/O operations asynchronously.

• E...read more

Design a system using Max Heap to find the costliest element from a box when an element is picked.

• Implement a Max Heap data structure to store the elements in the box.

• Whenever an element is picked, the costliest element can be found at the root of the Max Heap.

• After picking an element, update the Max Heap by removing the root and reorganizing the heap.

• Ensure the Max Heap property is maintained during insertion and deletion operations.

• Example: If the box contains elements [5, ...read more

When a server receives an HTTP request, it interacts with the operating system, handles threading, thread pooling, synchronization, and hashing.

• Upon receiving an HTTP request, the server creates a new thread to handle the request.

• The operating system manages the allocation of system resources to the server process.

• Thread pooling is used to efficiently manage and reuse threads for handling multiple requests.

• Synchronization mechanisms like locks or semaphores are used to ensure...read more

Program to determine if a graph is a tree using adjacency matrix

• A graph is a tree if it is connected and has no cycles

• Check if the graph is connected by performing a depth-first search or breadth-first search

• Check if the graph has cycles by performing a depth-first search and tracking visited nodes

The transaction process involves transferring funds from one account to another. A scheme is designed to ensure secure and accurate transfers.

• Verify the availability of sufficient funds in the sender's account

• Authenticate the sender's identity and authorization for the transaction

• Deduct the transfer amount from the sender's account balance

• Initiate a request to transfer the funds to the recipient's account

• Validate the recipient's account details

• Add the transferred amount to th...read more

Graphs are non-linear data structures with cycles while trees are hierarchical data structures without cycles.

• Graphs can have cycles while trees cannot

• Graphs can have multiple root nodes while trees have only one

• Graphs can have disconnected components while trees are always connected

• Graphs can have directed or undirected edges while trees have only directed edges

• Examples of graphs include social networks, road networks, and computer networks while examples of trees include fi...read more

LRU cache is a data structure that stores most recently used items and discards least recently used items.

• LRU stands for Least Recently Used

• It is implemented using a doubly linked list and a hash map

• When an item is accessed, it is moved to the front of the list

• When the cache is full, the least recently used item is removed from the end of the list

• Example: A web browser cache that stores recently visited web pages

A tree is a data structure consisting of nodes connected by edges, with a single root node and no cycles.

• Nodes represent elements of the tree, and edges represent the relationships between them.

• Each node can have zero or more child nodes, and each child node can have its own children.

• Trees are commonly used in computer science for organizing and searching data, such as in binary search trees.

• Examples of trees include file systems, family trees, and HTML document object models...read more

A graph can be called a tree if it is connected and has no cycles.

• A tree is a type of graph with no cycles.

• It must be connected, meaning there is a path between any two vertices.

• It has n-1 edges, where n is the number of vertices.

• Examples include family trees, file directory structures, and decision trees.

Typing amazon.com in the browser's address bar takes you to Amazon's website.

• The browser sends a request to the DNS server to resolve the domain name 'amazon.com' to an IP address.

• The browser establishes a TCP connection with the server at the resolved IP address.

• The browser sends an HTTP request to the server for the homepage of Amazon's website.

• The server responds with the HTML code for the homepage, which the browser renders and displays to the user.

Memory leakage is a situation where a program fails to release memory it no longer needs.

• Memory leakage can cause a program to slow down or crash due to insufficient memory.

• It is caused by programming errors such as not freeing allocated memory or losing references to it.

• Examples include forgetting to close a file or database connection, or not releasing memory allocated for a variable.

• Memory leakage can be detected using memory profiling tools.

• Preventing memory leakage invol...read more

To fix code that is working properly, first identify the problem, analyze the code, make necessary changes, and test thoroughly.

• Identify the problem by reproducing the issue and understanding the expected behavior.

• Analyze the code to find any logical errors, syntax issues, or performance bottlenecks.

• Make necessary changes by modifying the code, fixing bugs, optimizing algorithms, or enhancing functionality.

• Thoroughly test the modified code to ensure it works as expected and d...read more

ACID properties ensure reliability and consistency in database transactions.

• ACID stands for Atomicity, Consistency, Isolation, and Durability.

• Atomicity ensures that a transaction is treated as a single unit of work, either all or none of its operations are executed.

• Consistency ensures that a transaction brings the database from one valid state to another.

• Isolation ensures that concurrent transactions do not interfere with each other, providing a sense of isolation.

• Durability ...read more

OOPs stands for Object-Oriented Programming. It is a programming paradigm based on the concept of objects.

• Encapsulation: Bundling data and methods that operate on the data into a single unit.

• Inheritance: Ability of a class to inherit properties and behavior from another class.

• Polymorphism: Ability to present the same interface for different data types.

• Abstraction: Hiding the complex implementation details and showing only the necessary features.

BFS and DFS are graph traversal algorithms, while Prim's algorithm is used for finding minimum spanning tree in a weighted graph.

• BFS (Breadth First Search) visits nodes level by level, using a queue. Example: 1->2->3->4

• DFS (Depth First Search) explores as far as possible along each branch before backtracking. Example: 1->2->4->3

• Prim's algorithm finds the minimum spanning tree by starting from an arbitrary node and adding the closest edge at each step. Example: A->B, B->C, C->...read more

Fibonacci series can be generated using dynamic programming and recursion.

• Dynamic programming involves storing the values of previous calculations to avoid redundant calculations.

• Recursion involves calling the function within itself to generate the series.

• DP solution has O(n) time complexity while recursive solution has O(2^n) time complexity.

• DP solution uses an array to store the values while recursive solution uses function calls.

• Example DP solution: int fib[n+1]; fib[0]=0,...read more

final is a keyword used to declare constants in Java, while finally is a block used in exception handling to ensure code execution.

• final keyword is used to declare constants in Java classes or methods.

• final variables cannot be reassigned once initialized.

• finally block is used in exception handling to ensure code execution, regardless of whether an exception is thrown or not.

My main language for programming is Java.

• I have been using Java for over 5 years.

• I am proficient in object-oriented programming with Java.

• I have experience in developing web applications using Java frameworks like Spring and Hibernate.

Count the number of islands in a 2D grid of '1's (land) and '0's (water).

• Use Depth-First Search (DFS) or Breadth-First Search (BFS) to explore the grid.

• Mark visited land cells to avoid counting them multiple times.

• Iterate through each cell; if it's '1', increment the island count and explore its neighbors.

• Example: For grid [['1','1','0'], ['0','1','0'], ['0','0','0']], the output is 1.

Dynamic Programming (DP) is a technique to solve problems by breaking them down into smaller subproblems and solving them recursively.

• DP is used to solve optimization problems where we need to find the best solution among all possible solutions.

• DP problems can be solved using either top-down (memoization) or bottom-up (tabulation) approach.

• Recursion is a technique where a function calls itself to solve a problem. It is often used in DP problems.

• DP and recursion are closely re...read more

Implementing a tree data structure using code

• Define a Node class with left and right child pointers

• Implement insert, search, and delete functions

• Traversal methods: inorder, preorder, postorder

• Examples: binary search tree, AVL tree, red-black tree

Insertion sort is a simple sorting algorithm that builds the final sorted array one item at a time.

• Start with the second element and compare it with the first element, swap if necessary

• Move to the third element and compare it with the second and first element, swap if necessary

• Continue this process until the entire array is sorted

• Time complexity: O(n^2)

• Example: ['banana', 'apple', 'orange', 'grape'] -> ['apple', 'banana', 'grape', 'orange']

The expression would increment the value of i twice before using it in the operation.

• The value of i would be incremented by 2 before being used in the operation.

• This is equivalent to writing i = i + 2; followed by the operation using the new value of i.

• For example, if i was initially 3, the expression would evaluate to 6.