I received an invitation via email to attend Technology Early Insights Day, an event that was essentially a presentation about Morgan Stanley from their current engineers.

A few weeks later, I was invited for a final interview. I was interviewed by three engineers in an open-room setting, where other candidates were also being interviewed in the same venue.

A city had a network of traffic lights, and you were tasked to check whether any of them were not working. You were given two methods:

• One to find all neighboring traffic lights.
• Another to check if a particular traffic light is working.

Given an integer N, find the total sum of all numbers between 1 to N.