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This is a medium difficulty Coding & Algorithms question, commonly asked during Onsite rounds at Microsoft.

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This question is commonly asked for Machine Learning Engineer candidates at Microsoft during technical interviews.

Implement cache and merge intervals | Microsoft Coding Question

Quick Overview

This question evaluates proficiency in designing and implementing efficient data structures (a fixed-capacity LRU key-value cache) and interval-processing algorithms (merging overlapping closed intervals), emphasizing time-complexity constraints, correct state management, and robustness to edge cases within the Coding & Algorithms category.

Quick Overview

Implement cache and merge intervals

Company: Microsoft

Role: Machine Learning Engineer

Category: Coding & Algorithms

Difficulty: medium

Interview Round: Onsite

The interview included two coding tasks: 1. Implement a fixed-capacity key-value cache with `get(key)` and `put(key, value)`. Both operations must run in O(1) average time. When the cache is full and a new key is inserted, evict the least recently used entry. A successful `get` also counts as a use. 2. Given a list of closed intervals `[start, end]`, merge all overlapping intervals and return the resulting non-overlapping intervals sorted by start value.

Quick Answer: This question evaluates proficiency in designing and implementing efficient data structures (a fixed-capacity LRU key-value cache) and interval-processing algorithms (merging overlapping closed intervals), emphasizing time-complexity constraints, correct state management, and robustness to edge cases within the Coding & Algorithms category.

LRU Cache Operation Simulation

Simulate a fixed-capacity LRU cache. Return outputs for each operation, with None for put.

Constraints

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

Examples

Input: (2, [['put',1,1],['put',2,2],['get',1],['put',3,3],['get',2],['get',3]])

Expected Output: [None, None, 1, None, -1, 3]

Explanation: Evict least recently used key.

Input: (1, [['put',1,1],['put',1,2],['get',1]])

Expected Output: [None, None, 2]

Explanation: Updating key refreshes it.

Hints

Model object-style prompts as operation streams when needed.
Handle empty and boundary cases before the main logic.

Merge Closed Intervals

Merge overlapping closed intervals and return them sorted by start.

Constraints

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

Examples

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

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

Explanation: Prompt example.

Input: ([[1,4],[4,5]],)

Expected Output: [[1, 5]]

Explanation: Closed intervals touching overlap.

Input: ([],)

Expected Output: []

Explanation: No intervals.

Hints

Model object-style prompts as operation streams when needed.
Handle empty and boundary cases before the main logic.

Last updated: Jun 27, 2026

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