100+ SDE (Software Development Engineer) Interview Questions and Answers

Check if a string is a palindrome and can be made a palindrome by removing at most one character.

• Iterate through the string from both ends and check if the characters match.

• If the characters don't match, try removing one character from either end and check if the remaining string is a palindrome.

• If removing one character doesn't make the string a palindrome, then it's not possible to make it a palindrome by removing at most one character.

Implement 3 stacks using one array with optimized space and time complexity.

• Divide the array into three equal parts to represent each stack.

• Keep track of the top index of each stack separately.

• When pushing an element, increment the top index of the respective stack and store the element.

• When popping an element, retrieve the element from the top index of the respective stack and decrement the top index.

• Handle stack overflow and underflow conditions appropriately.

A startup is a newly established business that aims to solve a problem or meet a need using innovative technology.

• Startups are focused on growth and scalability.

• They often operate in a fast-paced and dynamic environment.

• Startups use various technologies depending on their industry and product.

• Common technologies used in startups include web and mobile development, cloud computing, data analytics, artificial intelligence, and blockchain.

• Examples of startup technologies include...read more

Waterfall model is a linear sequential approach to software development.

• Advantages: clear and well-defined stages, easy to understand and manage, suitable for small projects with stable requirements

• Disadvantages: inflexible, difficult to make changes once a stage is completed, testing is done only at the end, not suitable for large or complex projects

• Stages: requirements gathering, design, implementation, testing, deployment, maintenance

• Example: building a house, where each s...read more

Find most common ancestor nodes of a binary tree given two integers.

• Traverse the tree to find the nodes with the given integers

• Store the path from root to each node in separate arrays

• Compare the two arrays to find the most common ancestor node

• If there are multiple common ancestors, return the one closest to the root

Dutch National Flag algorithm can be used to sort an array of 0, 1, and 2 in O(n) time complexity and O(1) space complexity.

• Initialize three pointers: low, mid, and high.

• Iterate through the array and swap elements based on their values.

• Increment low and mid pointers when encountering 0.

• Increment mid pointer when encountering 1.

• Decrement high pointer when encountering 2.

Methods are functions that perform a specific task, while constructors are special methods that initialize objects.

• Constructors have the same name as the class they belong to.

• Constructors are called automatically when an object is created.

• Constructors can be overloaded with different parameters.

• Methods can be called multiple times with different arguments.

• Methods can have a return type, while constructors do not.

Finding an element in a rotated array

• Identify the pivot point where the array is rotated

• Divide the array into two sub-arrays based on the pivot point

• Perform binary search on the appropriate sub-array to find the element

• Handle edge cases like when the element is at the pivot point

Stacks are a data structure that follows the Last-In-First-Out (LIFO) principle.

• Stacks have two main operations: push (adds an element to the top) and pop (removes the top element).

• Stacks can be implemented using arrays or linked lists.

• Common applications of stacks include function call stack, undo/redo operations, and expression evaluation.

• Example: A stack of books, where the last book placed is the first one to be removed.

The given array needs to be flattened to a single-level array.

• Iterate through the array elements

• If an element is an array, recursively flatten it

• If an element is not an array, add it to the result array

Count the number of set bits in a given number.

• Use bitwise AND operator with 1 to check if the rightmost bit is set.

• Shift the number to right by 1 bit and repeat the process until the number becomes 0.

• Keep a count of the number of set bits encountered.

• Example: For number 5 (101 in binary), the answer is 2 as there are 2 set bits.

• Example: For number 15 (1111 in binary), the answer is 4 as there are 4 set bits.

Convert a number to its hexadecimal form

• Use the built-in function to convert the number to hexadecimal

• Alternatively, use the algorithm to convert the number to hexadecimal manually

• Ensure to handle negative numbers appropriately

Sort an array of 0s and 1s using O(n) solution.

• Use two pointers, one at the beginning and one at the end of the array.

• Swap the elements at the pointers if they are not in the correct order.

• Move the pointers towards each other until they meet in the middle.

• Time complexity is O(n) and space complexity is O(1).

Sorting a list of words with a random order using an alien dictionary

• Create a graph with nodes as characters and edges as the order of characters in words

• Topologically sort the graph to get the correct order of characters

• Use the order to sort the list of words

Yes, the project directory in Django follows a specific structure.

• The main project directory contains settings.py, urls.py, and wsgi.py files.

• Each app within the project has its own directory with models.py, views.py, and urls.py files.

• Static files are stored in a 'static' directory within each app.

• Templates are stored in a 'templates' directory within each app.

• Media files are stored in a 'media' directory within the project directory.

Singleton class is a class that can only have one instance at a time.

• Singleton pattern is used when we need to ensure that only one instance of a class is created and that instance can be accessed globally.

• The constructor of a singleton class is always private to prevent direct instantiation.

• A static method is used to access the singleton instance.

• Example: public class Singleton { private static Singleton instance = new Singleton(); private Singleton() {} public static Single...read more

Detect and remove cycle in a linked list

• Use two pointers, one slow and one fast, to detect a cycle

• Once a cycle is detected, move one pointer to the head and iterate both pointers until they meet again

• Set the next node of the last node in the cycle to null to remove the cycle

Find the maximum sum of a rectangle in a 2D matrix.

• Use Kadane's algorithm to find the maximum sum subarray in each row.

• Iterate over all possible combinations of rows and find the maximum sum rectangle.

• Keep track of the maximum sum and the coordinates of the rectangle.

Replace substring in a given string and print the remaining string

• Use string.replace() method to replace the substring

• Print the remaining string using string slicing

The choice of data structure depends on the type of data and the operations to be performed on it.

• Consider the size and complexity of the data

• Determine the operations to be performed on the data

• Choose a data structure that supports those operations efficiently

• Examples: arrays, linked lists, hash tables, trees, graphs

Polymorphism allows for flexibility and extensibility in code by enabling objects to take on multiple forms.

• Polymorphism allows for code reuse and simplifies maintenance.

• It enables the creation of generic code that can work with objects of different classes.

• It allows for the creation of interfaces and abstract classes, which can be implemented by multiple classes.

• Examples include using a parent class to represent multiple child classes, or implementing an interface to allow f...read more

Ingress is a Kubernetes resource that manages external access to services. Prometheus is a monitoring system and Grafana is a visualization tool.

• Ingress is used to route external traffic to the appropriate Kubernetes service

• Prometheus is used to collect and store metrics from various sources

• Grafana is used to visualize the collected metrics in a user-friendly way

• Ingress can be configured to use different load balancing algorithms

• Prometheus has a powerful query language for an...read more

To check if a string is palindrome or not.

• Compare the first and last characters of the string and continue towards the middle until all characters have been compared.

• If all characters match, the string is a palindrome.

• If any characters do not match, the string is not a palindrome.

To find length, frequency of each character and list of unique characters of a string.

• Iterate through the string and count the frequency of each character using a hash table.

• Create a list of unique characters by iterating through the hash table.

• Calculate the length of the string using the built-in length function.

• Return the frequency, length and list of unique characters as an array of strings.

The answer is -22

• Perform multiplication first

• Then perform addition and subtraction from left to right

Lexical scoping is a way of defining variable scope based on where they are declared in the code.

• Variables declared inside a function have local scope and are not accessible outside the function.

• Variables declared outside a function have global scope and can be accessed from anywhere in the code.

• Nested functions can access variables declared in their parent function.

• Example: function outer() { let x = 10; function inner() { console.log(x); } inner(); } outer(); // Output: 10

Answering which statement about a binary heap is false.

• A binary heap is a complete binary tree where the parent node is always greater or smaller than its children.

• A binary heap can be represented as an array.

• A binary heap can be used to implement priority queues.

• A binary heap can only be a max heap and not a min heap.