Research Scientist, Machine Learning (PhD)

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Write code to parse regular expressions including * (0 or more characters), + (1 or more characters), and . (1 exact character). For example: parse(a., ab) should return true. parse(a*, aaa) should return true. parse(a+, a) should return true. parse(a+, ) should return false. parse(a.*b, axyzb) should return true. parse(a.*b, axyz) should return false. parse(abc, abc) should return true. parse(abc, abd) should return false. Your function should take two strings as input: the regular expression and the string to match against. It should return a boolean indicating whether the string matches the regular expression. Focus on handling the special characters ., *, and +. Assume that other characters in the regular expression must match literally. Explain your approach and provide a clear, well-documented code implementation. Consider edge cases such as empty strings and null inputs. Also think about the time and space complexity of your solution, and try to optimize it for performance. Can you provide a solution using dynamic programming?

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Let's design a new feature for the Facebook app: Ephemeral Groups. These groups function like regular Facebook groups but with a key difference: all content (posts, comments, media) within the group is automatically deleted after 24 hours. The group itself remains, but the content vanishes. Imagine users creating groups for flash events, temporary project collaborations, or just sharing memes that are only funny for a day. Here are some considerations to guide our design: Use Cases: What are the primary use cases for Ephemeral Groups? Consider examples beyond those mentioned above. User Interface: How would users create and identify Ephemeral Groups within the existing Facebook app? How is it visually distinct? Data Storage: How would you efficiently store and automatically delete content to minimize storage costs and ensure compliance with the 24-hour expiration? Abuse Prevention: How do you prevent the misuse of Ephemeral Groups for sharing harmful or illegal content, given the disappearing nature of the data? Notifications: How would notifications work for Ephemeral Groups? Should users receive notifications for content that will disappear soon? Privacy: How would we make users aware of the ephemeral nature of the group and its content to manage their privacy expectations effectively? Scalability: How would this feature scale to handle potentially millions of Ephemeral Groups without impacting the performance of the overall Facebook platform? Walk me through your design proposal, addressing these considerations and any other relevant aspects you believe are important.

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Describe a time you had to work in an ambiguous environment. What was the situation, what actions did you take, and what was the result? Be specific and provide details about the ambiguity you faced. For example: Lack of Clear Requirements: Describe a project where the initial requirements were poorly defined or constantly changing. How did you navigate the uncertainty and ensure the project moved forward? Conflicting Information: Share an experience where you received conflicting information from different stakeholders. How did you reconcile these discrepancies and make informed decisions? Unclear Goals: Tell me about a time when the overall goals of a project or task were not well-defined. How did you work to clarify the objectives and achieve a successful outcome? Limited Resources: Describe a situation where you had to work with limited resources (time, budget, personnel). How did you prioritize your efforts and make the most of what you had available? New Technology or Domain: Share an experience where you had to work with a new technology or in a domain where you had limited prior experience. How did you quickly learn and adapt to the unfamiliar environment?