I applied online and about a month later was emailed asking to set up an hour-long phone interview.

The phone interview was between myself and a Facebook engineer. We used a program that allowed him to see me code in real-time.

A few days after the phone interview, I was emailed by the recruiter to inform me that they would not be pursuing my application further.

A museum was represented by a square matrix filled with 'O', 'G', and 'W'. 'O' represented open space, 'G' represented guards, and 'W' represented walls.

Write a function that accepts the square matrix and returns another square matrix where all of the 'O's are replaced with the number of spaces they are away from a guard, without being able to go through any walls.