# Digging a Canal

Simple+
English RU

The robots are trying to colonize a new island. There are many rivers on this island and it would be good idea for them to use ships designed for water, rather than their spaceships. Some of the territories do not have a river for transportation from one edge of a field to another. The robots can dig a canal and convert the land to water if need be. We must explore a field map and count the minimum number of cells necessary for a canal that would allow the robots to sail from northern edge of the map to southern edge. The map is in a 2D array, where 0 is water, 1 is land. Cells are connected by their edges.

Input: A map as a list of lists with 1 or 0.

Output: The minimum number of cells necessary for a canal as an integer.

Example:

```checkio([[1, 1, 1, 1, 0, 1, 1],
[1, 1, 1, 1, 0, 0, 1],
[1, 1, 1, 1, 1, 0, 1],
[1, 1, 0, 1, 1, 0, 1],
[1, 1, 0, 1, 1, 1, 1],
[1, 0, 0, 1, 1, 1, 1],
[1, 0, 1, 1, 1, 1, 1]]) == 2
checkio([[0, 0, 0, 0, 0, 0, 0],
[1, 1, 1, 1, 1, 1, 1],
[1, 1, 1, 1, 1, 1, 1],
[1, 1, 1, 1, 1, 1, 1],
[1, 1, 0, 1, 0, 1, 1],
[1, 0, 0, 0, 0, 0, 1],
[0, 0, 0, 0, 0, 0, 0]]) == 3
checkio([[1, 1, 1, 1, 1, 0, 1, 1],
[1, 0, 1, 1, 1, 0, 1, 1],
[1, 0, 1, 0, 1, 0, 1, 0],
[1, 0, 1, 1, 1, 0, 1, 1],
[0, 0, 1, 1, 0, 0, 0, 0],
[1, 0, 1, 1, 1, 1, 1, 1],
[1, 0, 1, 1, 1, 1, 1, 1],
[1, 1, 1, 0, 1, 1, 1, 1]]) == 2
```

How it is used: This concept is a mix of graph-search and optimization problems. It can be useful in navigational software and for network optimization.

Precondition: 0 < len(land_map) < 10
all(0 < len(row) < 10 for row in land_map)

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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`

`checkio --domain=py config --key=`

Sync solutions into your local folder

`checkio sync`

(in beta testing) Launch local server so your browser can use it and sync solution between local file end extension on the fly. (doesn't work for safari)

`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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