Roblox Phone Screen
Summary
I recently had a phone screen with Roblox where I was given a complex problem involving optimizing avatar load times. The challenge was to determine the correct loading order for avatar components, considering their dependencies and preserving the relative input order.
Full Experience
During my phone screen at Roblox, I was presented with an interesting problem related to optimizing avatar load times on their platform. The interviewer described a scenario where each avatar consists of multiple components (body parts, accessories, animations, etc.). Some components may depend on others, for instance, a specific hat can only be loaded after the head and hair. My task was to design an algorithm to correctly determine the loading order of these components, ensuring all dependencies are respected. A key constraint was to preserve the relative order of the input components if multiple valid orderings existed. I also had to handle cases of circular or missing dependencies by returning an error. The problem provided several examples illustrating different dependency scenarios and their expected outputs. It was a good test of my understanding of graph algorithms and dependency resolution, specifically a variation of topological sort.
Interview Questions (1)
You are tasked with optimizing avatar load times for experiences on the Roblox platform. Each avatar comprises multiple components (body parts, accessories, animations, etc.). Some components may depend on others (e.g., a specific hat can only be loaded after the head and hair). Given a list of components and their dependencies, design an algorithm that determines the correct loading order for the avatar's components, ensuring all dependencies are respected. If multiple orderings exist, return the one preserving the relative order of the input. If circular or missing dependencies exist, return an error.
Input/Output Format Input: a list of components and dependencies, expressed as multiple lists of strings. Each string list contains the component's name as the first element and is followed by an arbitrary number of strings representing dependent components. Output: a list of components sorted by the order in which they need to be loaded, or a list with a single element "Error!" if no solution exists.
Example 1: Input: [ ["Head"], ["Torso"], ["Legs"] ]
Output: ["Head", "Torso", "Legs"]
Explanation: The 3 components don't have any dependency and therefore we can just return them in their original order.
Example 2: Input: [ ["Hair","Head"], ["Hat","Hair"], ["Head"] ]
Output: ["Head", "Hair", "Hat"]
Explanation: Hair is dependent on Head and therefore must be loaded after it. Hat is dependent on Hair and therefore must be loaded after it. This suggests the ordering Head, Hair, Hat.
Example 3: Input: [ ["Hair","Head"], ["Head","Hair"] ]
Output: ["Error!"]
Explanation: Hair is dependent on Head and vice versa. Therefore no valid ordering exists and we return an error.
Example 4: Input: [ ["Hair","Head"], ["Head"], ["Torso"], ["Arm","Torso"] ]
Output: ["Head", "Hair", "Torso", "Arm"]
Explanation: Hair is dependent on Head and must come after it. Arm is dependent on Torso and must come after it. With only these constraints, multiple orders are possible (e.g. Head, Hair, Torso, Arm, or Torso, Arm, Head, Hair or even Head, Torso, Hair, Arm. However, since we must preserve the relative order of the input, the correct order is Head, Hair, Torso, Arm.