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This is a Medium difficulty Coding & Algorithms question, commonly asked during Technical Screen rounds at Meta.

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This question is commonly asked for Software Engineer candidates at Meta during technical interviews.

Solve BST range average and merge intervals

Quick Overview

This question evaluates understanding of binary search tree properties and range-based traversal pruning for computing aggregates, together with techniques for merging two sorted interval lists into non-overlapping ranges, testing proficiency with tree and interval data structures and aggregate computation in the Coding & Algorithms domain.

Company: Meta

Role: Software Engineer

Category: Coding & Algorithms

Difficulty: Medium

Interview Round: Technical Screen

1) Given a binary search tree and an inclusive range [L, R], compute both the sum and the average of all node values where L <= val <= R. Use the BST property to prune traversal. Implement sumAndAverageInRange(root, L, R) -> (sum: int, average: float). Specify how to handle the case when no nodes fall in the range, and analyze time/space complexity. 2) Given two lists of intervals A and B, each list sorted by start time in ascending order (intervals are [start, end] with start <= end), merge them into a single list of non-overlapping intervals covering all intervals from A ∪ B. Clarify whether touching intervals (e.g., [1,3] and [3,5]) should be merged, handle potentially overlapping intervals within and across lists, implement mergeTwoSortedIntervalLists(A, B), and analyze complexity.

Quick Answer: This question evaluates understanding of binary search tree properties and range-based traversal pruning for computing aggregates, together with techniques for merging two sorted interval lists into non-overlapping ranges, testing proficiency with tree and interval data structures and aggregate computation in the Coding & Algorithms domain.

BST Range Sum and Average

Use BST pruning on level-order values to return the sum and average of values in inclusive range [L,R].

Constraints

Inputs are Python literals matching the function signature.
Return a deterministic exact-match value.

Examples

Input: ([10,5,15,3,7,None,18], 7, 15)

Expected Output: {'sum': 32, 'average': 10.666666666666666}

Explanation: Range includes 7,10,15.

Input: ([5], 6, 9)

Expected Output: {'sum': 0, 'average': None}

Explanation: No values in range.

Input: ([], 1, 2)

Expected Output: {'sum': 0, 'average': None}

Explanation: Empty tree.

Hints

Choose a representation that makes the requested operation direct.
Handle empty inputs and boundary cases first.

Merge Two Sorted Interval Lists

Merge two sorted interval lists into one non-overlapping list, merging touching intervals.

Constraints

Inputs are Python literals matching the function signature.
Return a deterministic exact-match value.

Examples

Input: ([[1,3],[8,10]], [[2,6],[15,18]])

Expected Output: [[1, 6], [8, 10], [15, 18]]

Explanation: Cross-list overlap.

Input: ([[1,3]], [[3,5]])

Expected Output: [[1, 5]]

Explanation: Touching intervals merge.

Input: ([], [[1,2]])

Expected Output: [[1, 2]]

Explanation: One list empty.

Hints

Choose a representation that makes the requested operation direct.
Handle empty inputs and boundary cases first.

Quick Overview