# Nearest neighbour algorithm
[](https://travis-ci.org/HenrikFricke/elixir-nearest-neighbour-algorithm)
> [Nearest neighbour algorithm](https://en.wikipedia.org/wiki/Nearest_neighbour_algorithm)
written in Elixir.
## Installation
1. Add `nearest_neighbour_algorithm` to your list of dependencies in `mix.exs`:
```elixir
def deps do
[{:nearest_neighbour_algorithm, "~> 1.0.2"}]
end
```
## Usage
Based on the [Travelling salesman problem](https://en.wikipedia.org/wiki/Travelling_salesman_problem) we create a list with all points, where we want to find the shortest route between them.
Example:
```elixir
iex> map = [
a: [a: 0.00, b: 5.12, c: 3.40, d: 9.63, e: 6.81],
b: [a: 5.12, b: 0.00, c: 4.91, d: 6.85, e: 8.42],
c: [a: 3.40, b: 4.91, c: 0.00, d: 6.67, e: 3.87],
d: [a: 9.63, b: 6.85, c: 6.67, d: 0.00, e: 6.88],
e: [a: 6.81, b: 8.42, c: 3.87, d: 6.88, e: 0.00]
]
iex> NearestNeighbourAlgorithm.shortest_route(map)
[:a, :c, :e, :d, :b, :a]
```
As you can see the map describes the distances between the points, it's
the same like the following table:
| | A | B | C | D | E |
|:---:|:---:|:---:|:---:|:---:|:---:|
| A | 0 | 5.12| 3.4 | 9.63| 6.81|
| B | 5.12| 0 | 4.91| 6.85| 8.42|
| C | 3.4 | 4.91| 0 | 6.67| 3.87|
| D | 9.63| 6.85| 6.67| 0 | 6.88|
| E | 6.81| 8.42| 3.87| 6.88| 0 |
The algorithm will start to the first point, which is `:a` in our example. Then it will look up the nearest neighbour of `:a`, which is `:c`. He will move to `:c` and repeat the steps until every point has been reached. So in our example the shortest route is:
A - C - E - D - B - A.
## License
The MIT License (MIT)
Copyright (c) 2016 Henrik Fricke
Permission is hereby granted, free of charge, to any person obtaining a copy
of this software and associated documentation files (the "Software"), to deal
in the Software without restriction, including without limitation the rights
to use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies
of the Software, and to permit persons to whom the Software is furnished to do
so, subject to the following conditions:
The above copyright notice and this permission notice shall be included in all
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THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
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