Applied and was sent a HackerRank challenge.

It consisted of 3 questions to be completed in 90 minutes.

The questions seemed to be one LeetCode easy, one medium, and one hard.

I missed 4 test cases on the last one due to time complexity and received a rejection the next day.

Given a number line from 0 to n and a string denoting a sequence of moves, determine the number of subsequences of those moves that lead from a given point x to end at another point y.

Moves will be given as a sequence of 'l' and 'r' instructions.

• An instruction 'l' means a left movement, so from position j the new position is j - 1.
• An instruction 'r' means a right movement, so from position j the new position would be j + 1.