Ola Interview Experience (1 Year Experienced)

I applied to OLA through referral for the position of SDE1.

Round 1 (F2F Virtual Interview): 4 DS Algo questions(codepair round on hackerrank).

1. Reverse an array.
2. Rain Water Trapping problem.
3. Minimum time needed to burn a tree starting from a node.
4. Minimum cost for joining ropes of different length. (Follow up:Implement your own heap).

Round 2(F2F Virtual Interview): 3 DS Algo questions(share screen and code) .

1. Generate all permutation of a string.
2. Generate all distinct permutations of a string.
3. Generate next smallest permutation of a number. - Similar problem

Round 3(F2F Virtual Interview): 2 DS Algo questions(share screen and code).

1. Given a n*m grid of different characters, check if a cycle of size greater than three exists.(cycle must contain similar characters, consider left right up bottom character as neighbour)
2. Product of Array Except Self.

Round 4(F2F Hiring Manager round):

• Introduce yourself.
• Questions related to my project.
• Questions on scaling(Vertical scaling vs horizontal scaling).
• Questions on SQL vs NOSQL.
• Types of HTTPs method.
• Difference between PUT and POST.
• How would you search all the numbers common in a small file and a big file.
• What DS would you use while creating your own hashing algorithm.
• Some behavioural questions.

For all DSA question they asked to explain the approach first and then code. In between lot of cross question was asked.