Site Reliability Engineer L4/L5 - Live Streaming Pipeline

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You are given the definition of a binary tree node: class Node: def init(self, val=0, left=None, right=None): self.val = val self.left = left self.right = right Write a function is_bst(root) that takes the root of a binary tree as input and returns True if the tree is a valid Binary Search Tree (BST), and False otherwise. Definition of a BST: The left subtree of a node contains only nodes with keys less than the node's key. The right subtree of a node contains only nodes with keys greater than the node's key. Both the left and right subtrees must also be binary search trees. Example 1: Input: root = [2,1,3] Output: true 2 / 1 3 Example 2: Input: root = [5,1,4,null,null,3,6] Output: false 5 / 1 4 / 3 6 Explanation: The root node's value is 5 but its right child's value is 4. Constraints: The number of nodes in the tree is in the range [1, 10000]. -10000 <= Node.val <= 10000 Your solution should handle edge cases such as an empty tree or a tree with only one node.

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Let's delve into the Observer pattern. Imagine you're building a stock market application. You have a central Stock object that holds the current price. Multiple components, such as a PriceDisplay, a Graph, and an AlertSystem, need to update whenever the Stock price changes. Explain the Observer pattern: Describe the core components (Subject, Observer) and how they interact. Explain the benefits of using this pattern in scenarios like the stock market application. Design Implementation: Provide a simplified code implementation of the Observer pattern for this stock market scenario. Show how the Stock object (Subject) would manage its observers (PriceDisplay, Graph, AlertSystem) and how these observers would receive updates when the stock price changes. Focus on clarity and demonstrating the core concepts. Trade-offs: What are the potential drawbacks of using the Observer pattern, especially in a system with a large number of observers? How might you mitigate these issues (e.g., using weak references, asynchronous updates)? Alternatives: Are there alternative patterns or approaches you might consider instead of the Observer pattern for this type of scenario? What are the pros and cons of these alternatives compared to the Observer pattern? Real-world Examples: Besides a stock market application, can you describe other real-world examples where the Observer pattern is commonly used?

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Tell me about a time you had to make a difficult decision with incomplete information. What was the situation? What information was missing? What decision did you make and how did you arrive at it? What was the outcome? What did you learn from the experience? For example, perhaps you had to decide whether to launch a new feature without complete user testing data, or whether to pursue a new market opportunity without a full understanding of the competitive landscape. Maybe you had to make a critical hiring decision without all the information you needed about the candidate's past performance. The key is to show that you can assess risks, weigh potential outcomes, and make sound judgments even when things are uncertain. Be sure to articulate the reasoning that led you to your decision, and reflect on the lessons you learned from the experience. This demonstrates your adaptability, problem-solving abilities, and your capacity for learning and growth.