{ "data": { "question": { "questionId": "883", "questionFrontendId": "853", "boundTopicId": null, "title": "Car Fleet", "titleSlug": "car-fleet", "content": "

There are n cars going to the same destination along a one-lane road. The destination is target miles away.

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You are given two integer array position and speed, both of length n, where position[i] is the position of the ith car and speed[i] is the speed of the ith car (in miles per hour).

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A car can never pass another car ahead of it, but it can catch up to it and drive bumper to bumper at the same speed. The faster car will slow down to match the slower car's speed. The distance between these two cars is ignored (i.e., they are assumed to have the same position).

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A car fleet is some non-empty set of cars driving at the same position and same speed. Note that a single car is also a car fleet.

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If a car catches up to a car fleet right at the destination point, it will still be considered as one car fleet.

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Return the number of car fleets that will arrive at the destination.

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Example 1:

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\nInput: target = 12, position = [10,8,0,5,3], speed = [2,4,1,1,3]\nOutput: 3\nExplanation:\nThe cars starting at 10 (speed 2) and 8 (speed 4) become a fleet, meeting each other at 12.\nThe car starting at 0 does not catch up to any other car, so it is a fleet by itself.\nThe cars starting at 5 (speed 1) and 3 (speed 3) become a fleet, meeting each other at 6. The fleet moves at speed 1 until it reaches target.\nNote that no other cars meet these fleets before the destination, so the answer is 3.\n
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Example 2:

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\nInput: target = 10, position = [3], speed = [3]\nOutput: 1\nExplanation: There is only one car, hence there is only one fleet.\n
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Example 3:

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\nInput: target = 100, position = [0,2,4], speed = [4,2,1]\nOutput: 1\nExplanation:\nThe cars starting at 0 (speed 4) and 2 (speed 2) become a fleet, meeting each other at 4. The fleet moves at speed 2.\nThen, the fleet (speed 2) and the car starting at 4 (speed 1) become one fleet, meeting each other at 6. The fleet moves at speed 1 until it reaches target.\n
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Constraints:

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Compiled with clang 11 using the latest C++ 20 standard.

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Your code is compiled with level two optimization (-O2). AddressSanitizer is also enabled to help detect out-of-bounds and use-after-free bugs.

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Most standard library headers are already included automatically for your convenience.

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OpenJDK 17. Java 8 features such as lambda expressions and stream API can be used.

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Most standard library headers are already included automatically for your convenience.

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Includes Pair class from https://docs.oracle.com/javase/8/javafx/api/javafx/util/Pair.html.

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Python 2.7.12.

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For Map/TreeMap data structure, you may use sortedcontainers library.

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C# 10 with .NET 6 runtime

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Node.js 16.13.2.

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Ruby 3.1

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Some common data structure implementations are provided in the Algorithms module: https://www.rubydoc.info/github/kanwei/algorithms/Algorithms

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Swift 5.5.2.

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Go 1.21

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Python 3.10.

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Dart 2.17.3

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