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

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

Minimize exact layover bookings | Airbnb Coding Question

Quick Overview

This question evaluates algorithmic problem-solving and numeric precision handling, specifically the ability to model exact-duration sums and minimize the number of bookings under strict equality constraints.

medium
Airbnb
Coding & Algorithms
Machine Learning Engineer

Minimize exact layover bookings

Company: Airbnb

Role: Machine Learning Engineer

Category: Coding & Algorithms

Difficulty: medium

Interview Round: Onsite

You are given a layover length `X` in hours and a list of available experience durations, where every value has exactly one decimal place. You want to spend exactly `X` hours on booked experiences. Rules: - You may book the same experience multiple times. - The total booked duration must equal `X` exactly. - Among all exact combinations, return the minimum number of bookings. - If no exact combination exists, return `0`. Example: - `durations = [3.0, 2.0]` - `X = 7.0` - Output: `3`, because `2.0 + 2.0 + 3.0 = 7.0` Explain your approach and handle decimal precision robustly.

Quick Answer: This question evaluates algorithmic problem-solving and numeric precision handling, specifically the ability to model exact-duration sums and minimize the number of bookings under strict equality constraints.

You are given a layover length X in hours and a list of available experience durations. Every duration and X has exactly one decimal place. You may book any experience multiple times. Find the minimum number of bookings needed so that the total booked duration is exactly X hours. If no exact combination exists, return 0. Because the values are decimal numbers, your implementation should avoid direct floating-point equality checks and handle precision robustly.

Constraints

0 <= len(durations) <= 200
0.0 <= X <= 1000.0
Each duration is greater than 0 and has exactly one decimal place
You may reuse any duration an unlimited number of times

Examples

Input: ([3.0, 2.0], 7.0)

Expected Output: 3

Explanation: Book durations 2.0, 2.0, and 3.0 to reach exactly 7.0 hours with 3 bookings.

Input: ([1.0, 3.0, 4.0], 6.0)

Expected Output: 2

Explanation: The best exact combination is 3.0 + 3.0 = 6.0, which uses 2 bookings.

Input: ([0.1, 0.2, 0.5], 0.7)

Expected Output: 2

Explanation: Using 0.2 + 0.5 reaches 0.7 exactly with only 2 bookings. This case checks decimal precision handling.

Input: ([2.2, 4.4], 3.3)

Expected Output: 0

Explanation: No combination of 2.2 and 4.4 can add up to exactly 3.3.

Input: ([], 5.0)

Expected Output: 0

Explanation: With no available experiences, it is impossible to reach 5.0 hours.

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Quick Overview

Minimize exact layover bookings

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Examples

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