Freecharge Backend Developer Interview Questions and Answers

Minimum cost to reach last cell of 2D matrix with only downward or right moves.

• Use dynamic programming approach to solve the problem.

• Calculate minimum cost for each cell by considering minimum cost of its adjacent cells.

• Final answer will be the minimum cost to reach the last cell.

Design a stack that supports getMin functionality to return the minimum element in the stack.

• Create two stacks, one for storing the actual elements and another for storing the minimum elements.

• Push elements onto both stacks simultaneously.

• When popping an element, pop from both stacks.

• To get the minimum element, peek at the top of the minimum stack.

TreeSet is a data structure that stores unique elements in sorted order.

• TreeSet is implemented using a Red-Black tree

• It provides O(log n) time complexity for basic operations like add, remove, and contains

• It also provides methods like first(), last(), headSet(), tailSet(), and subSet()

• TreeSet can be used to implement priority queues and sorting algorithms

Design an ArrayList with getMax functionality.

• Create a custom ArrayList class that extends the existing ArrayList class.

• Add a getMax() method that returns the maximum value in the list.

• Override the add() method to keep track of the maximum value in the list.

• Update the maximum value whenever an element is added or removed from the list.

To find the maximum water pond formed between buildings.

• Identify the lowest point between the buildings.

• Calculate the area of the pond using the distance between the buildings and the depth of the pond.

• Consider any obstacles or uneven ground that may affect the pond's shape.

• Use a surveying tool or satellite imagery to get accurate measurements.

• Take into account any drainage systems or natural water flow that may affect

Design a dictionary using trie with insert, update and delete operations.

• Implement a Trie data structure with nodes containing a character and a boolean flag to indicate end of word

• For insert operation, traverse the trie and add nodes for each character in the word

• For update operation, delete the existing word and insert the updated word

• For delete operation, mark the end of word flag as false and delete the node if it ...read more

Find the odd repeating element from an array of strings

• Use a hash table to count the frequency of each element

• Iterate through the hash table to find the element with an odd count

Finding an element in a sorted 2D matrix

• Start from the top right corner or bottom left corner

• Compare the target element with the current element

• Move left or down if the target is smaller, else move right or up

• Repeat until the target is found or all elements are checked

SQL query to find Nth highest salary from table

• Use ORDER BY and LIMIT clauses

• Use subquery to get the Nth highest salary

• Handle cases where there are less than N distinct salaries

Function to swap '3' and '4' without using if-else

• Use XOR operator to swap the values

• Convert the input to ASCII code and perform the swap

• Use a lookup table to map the values

I am a software developer with experience in Java and Python.

• Proficient in Java and Python programming languages

• Experience in developing web applications using Spring framework

• Familiarity with database management systems like MySQL and MongoDB

PAYTM is a leading digital payment platform in India with a wide range of services.

• PAYTM has a user-friendly interface and offers a seamless payment experience.

• It provides a variety of services like mobile recharges, bill payments, and online shopping.

• PAYTM has a strong focus on security and fraud prevention measures.

• It has a large user base and is widely accepted by merchants across India.

• PAYTM is constantly innovatin...read more

Yes, I am open to pursuing further studies in the future.

• I believe in continuous learning and staying updated with the latest technologies.

• Further studies can help me specialize in a particular field and enhance my skills.

• I may consider pursuing a master's degree in computer science or a related field.

• However, my immediate focus is on gaining practical experience and contributing to the organization.

PAYTM grew fast due to its innovative approach and early adoption of digital payments.

• Early adoption of digital payments in India

• Innovative approach with features like mobile recharges, bill payments, and cashback offers

• Expansion into e-commerce and financial services

• Strategic partnerships with major companies like Uber and Alibaba