BT Group Interview Questions and Answers

The minimum number of platforms needed to avoid train crashes based on arrival and departure times.

• Sort the arrival and departure arrays in ascending order.

• Initialize a variable to keep track of the maximum number of platforms needed.

• Iterate through the arrival and departure arrays simultaneously.

• If the current arrival time is less than or equal to the current departure time, increment the platform count.

• If the current arrival time is greater than the current departure time, ...read more

Find two missing numbers from an unsorted array in O(n) time complexity.

• Calculate the sum of all numbers from 1 to n using the formula n*(n+1)/2

• Calculate the sum of all numbers in the given array

• Subtract the sum of array from the sum of all numbers to get the sum of missing numbers

• Use the sum of missing numbers and the sum of squares of all numbers from 1 to n to calculate the missing numbers using simultaneous equations

Divide a golden brick into minimum parts to pay daily salary to a worker.

• The number of parts needed will depend on the daily salary of the worker.

• The size of the parts should be equal.

• The parts should be small enough to cover the daily salary but large enough to minimize the number of parts.

• The formula to calculate the number of parts is: number of parts = total value of the golden brick / daily salary

Cut the cake in half horizontally and vertically to get 4 equal shape parts.

• Cut the cake in half horizontally.

• Cut the cake in half vertically.

• Arrange the resulting pieces to form 4 equal shape parts.

• Ensure each part has the same amount of cake.

• Use a knife or cake slicer to make the cuts.

• Be careful not to break the cake while cutting.

To find average salary without disclosing any one salary

• Collect salaries of all employees

• Add all salaries and divide by total number of employees

• Do not disclose any individual salary

To find the right view of a binary tree, we need to traverse the tree and keep track of the rightmost node at each level.

• Traverse the tree using level order traversal

• At each level, keep track of the rightmost node

• Add the rightmost node to the result array

• Return the result array

Remove duplicates from array of strings in place

• Use a HashSet to keep track of unique elements

• Iterate through the array and remove duplicates by checking if element is already in the HashSet

• Update the array in place by shifting elements to fill in the removed duplicates

Twitter system design involves multiple components such as servers, databases, caching, and APIs.

• Use sharding to distribute data across multiple servers

• Implement caching to reduce database load

• Use message queues for handling high traffic

• Implement APIs for user authentication and data retrieval

• Use load balancers to distribute traffic evenly

• Implement a search engine for efficient search functionality