Fast Train Fast Train

You are planning the train schedule and you want to know the minimum time of traveling between the stations.

Each section of the rail between stations is given in the list. Each section is a tuple of distance and speed limit (both are integers). You can change the speed ( +1. -1 and ± 0 ) at the start and every minute after that. The train runs by the same amount as the speed value in a minute.
Note: This means that a train with a speed 2 will travel a distance 2 before another minute passes and its speed can be changed again.

  • Starting speed is 0.
  • Speed limit is set for each section of the rail. You don't exceed it.
  • You must reach the target station at speed 1 (because it’s necessary to stop at the station).

You should return the minimum time (minutes) as an integer.



fast_train([(4, 3)]) == 3 # (1, 2, 1)
fast_train([(9, 5)]) == 5 # (1, 2, 3, 2, 1)
fast_train([(5, 5), (4, 2)]) == 6 # e.g. (1, 2, 2, 2, 1, 1)

Input: A list of the section of the rail. Each section is a tuple of distance (as an integer) and speed limit (as an integer).

Output: The minimum time (minutes) as an integer.

How it is used:
For efficient acceleration and deceleration.


  • distance > 0
  • speed limit > 0
  • len(section) > 0

CheckiO Extensions

CheckiO Extensions allow you to use local files to solve missions. More info in a blog post.

In order to install CheckiO client you'll need installed Python (version at least 3.8)

Install CheckiO Client first:

pip3 install checkio_client

Configure your tool

checkio --domain=py config --key=

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checkio sync

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checkio serv -d

Alternatevly, you can install Chrome extension or FF addon

checkio install-plugin
checkio install-plugin --ff
checkio install-plugin --chromium

Read more here about other functionality that the checkio client provides. Feel free to submit an issue in case of any difficulties.

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