Junior Backend Developer

Junior Backend Developer Interview Questions and Answers

Updated 24 May 2024
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Q1. 4. Basic Difference between Trees and Graph and the way we can traverse them

Ans.

Trees are a type of graph with a hierarchical structure. Graphs are a collection of nodes and edges.

  • Trees have a single root node, while graphs can have multiple disconnected nodes.

  • Traversal of trees can be done using depth-first or breadth-first search algorithms.

  • Traversal of graphs can be done using various algorithms like Dijkstra's algorithm, Bellman-Ford algorithm, etc.

Q2. What is update query in SQL to update data?

Ans.

The UPDATE query is used to modify existing data in a database table.

  • The UPDATE query is followed by the name of the table and the SET keyword to specify the columns to be updated.

  • The WHERE clause is used to specify the condition for updating specific rows.

  • Multiple columns can be updated in a single UPDATE query.

  • The UPDATE query can be used with various operators like =, +, -, *, /, etc.

  • Example: UPDATE employees SET salary = 50000 WHERE department = 'IT';

Q3. 2. Convert a Binary Tree into an inverted Binary Tree

Ans.

Invert a given binary tree by swapping left and right child nodes recursively.

  • Recursively swap left and right child nodes of each node in the binary tree.

  • Start from the root node and swap its left and right child nodes.

  • Then, recursively swap the left and right child nodes of the left and right child nodes of the root node.

  • Repeat the process until all nodes have been swapped.

  • Return the inverted binary tree.

Q4. How to kill a process in linux?

Ans.

Use the 'kill' command followed by the process ID to terminate a process in Linux.

  • Use 'ps' command to find the process ID of the process you want to kill

  • Use 'kill' command followed by the process ID to terminate the process

  • You can also use 'kill -9' followed by the process ID for a forceful termination

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Q5. What is PATCH method in HTTP?

Ans.

PATCH method in HTTP is used to partially update a resource on the server.

  • PATCH requests are used to make partial updates to a resource

  • It is typically used when you want to update only a few fields of an existing resource

  • The PATCH request body contains the changes to be applied to the resource

Q6. What is teh structure of JWT?

Ans.

JWT (JSON Web Token) is a compact, URL-safe means of representing claims to be transferred between two parties.

  • JWT consists of three parts: header, payload, and signature.

  • Header typically consists of the type of token and the signing algorithm being used.

  • Payload contains the claims. Claims are statements about an entity (typically the user) and additional data.

  • Signature is created by encoding the header, payload, a secret, and the algorithm specified in the header.

  • JWTs are ty...read more

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Q7. different between linkdlist and aarylist

Ans.

LinkedList is a data structure where each element points to the next element, while ArrayList is a resizable array implementation.

  • LinkedList uses pointers to connect elements, while ArrayList uses an underlying array to store elements.

  • LinkedList allows for efficient insertion and deletion of elements, while ArrayList is more efficient for random access.

  • LinkedList is not contiguous in memory, while ArrayList is contiguous in memory.

  • Example: LinkedList: 1 -> 2 -> 3 -> 4, ArrayL...read more

Q8. Why do we use CORS?

Ans.

CORS is used to allow or restrict cross-origin requests in web applications.

  • CORS is used to prevent malicious websites from making unauthorized requests to a different origin.

  • It allows servers to specify who can access their resources by setting appropriate headers.

  • CORS is important for security and privacy reasons in web development.

  • Example: If a frontend application on domain A wants to make a request to a backend API on domain B, CORS must be implemented to allow this comm...read more

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Q9. any program of recursion

Ans.

Recursion is a programming technique where a function calls itself in order to solve a problem.

  • Recursion involves breaking down a problem into smaller subproblems and calling the function recursively on each subproblem.

  • Base case is important in recursion to prevent infinite loop.

  • Examples of recursive functions include factorial calculation, Fibonacci sequence generation, and tree traversal.

Q10. write code for shorting

Ans.

Code for sorting an array of strings

  • Use a sorting algorithm like bubble sort, selection sort, or quicksort

  • Implement the sorting algorithm in a function that takes an array of strings as input

  • Return the sorted array of strings

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