Freecharge Interview Questions and Answers for Freshers

Whatsapp low level design involves messaging, encryption, media sharing, and user authentication.

• Use end-to-end encryption to secure messages

• Implement message queues for real-time message delivery

• Allow media sharing through file transfer protocols

• Use OAuth for user authentication and authorization

Remove the kth node from the end of a linked list.

• Use two pointers, one to traverse the list and another to keep track of the kth node from the end.

• Once the first pointer reaches the end, the second pointer will be at the kth node from the end.

• Adjust the pointers to remove the kth node.

Finding the stock price with maximum profit.

• Calculate the difference between each day's stock price and the minimum stock price seen so far.

• Find the maximum difference calculated in the previous step.

• The maximum difference is the maximum profit that can be made.

• Add the maximum difference to the minimum stock price to get the stock price with maximum profit.

Calculate the number of subsets of a given set

• The number of subsets of a set with n elements is 2^n

• Include the empty set and the set itself in the count

• For example, a set with 3 elements will have 2^3 = 8 subsets

To count the number of zeroes at the end of an array.

• Loop through the array from the end and count the number of zeroes until a non-zero element is encountered.

• Use a while loop to keep dividing the last element by 10 until it is not divisible by 10 to count the number of zeroes.

• If the array is sorted in non-increasing order, use binary search to find the last non-zero element and subtract its index from the length of the array.

A Dockerfile is a text document that contains all the commands a user could call on the command line to assemble an image.

• Start with a base image using the FROM keyword

• Use the RUN keyword to execute commands in the container

• Use the COPY keyword to add files from the host machine to the container

• Use the CMD keyword to specify the command to run when the container starts

File system in Linux organizes and manages data on storage devices.

• File system controls how data is stored, accessed, and managed on storage devices.

• Linux uses a hierarchical file system structure with directories and files.

• Common file systems in Linux include ext4, XFS, and Btrfs.

• File permissions in Linux determine who can read, write, or execute files.

• Mounting and unmounting drives allows access to different file systems on Linux.

Find pairs in array that sum up to a given target value.

• Iterate through the array and store each element in a hash set.

• For each element, check if the target value minus the current element exists in the hash set.

• Return the pair of elements that sum up to the target value.