I had four technical interviews (two pairs) and an HR interview. All of them on-site and lasted 1.5-3 hours.

After I finished the process, I was told by the recruiter that they want to move on to the proposal, but they need to get authorization from the headquarters. So we waited and waited and waited... At last after almost two weeks they said that they didn't get authorization to hire for this position.

The whole process was very pleasant for me, up until the end. I honestly can't understand how a self respecting company would publish a job posting without knowing it's able to hire for the published position, let along dragging a person to three long on-site interviews.

It was a big disappointment for me and felt like a complete disrespect of my very precious time.

Design a sudoku solver

Check if a binary tree is a search tree

Designing another game - also recursive solution.

Given several starting points and end points to a graph, find the longest path to get to each end point.