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# Toposort
Sort directed acyclic graphs
[](https://travis-ci.org/marcelklehr/toposort)
## Installation
`npm install toposort` or `component install marcelklehr/toposort`
then in your code:
```js
toposort = require('toposort')
```
## Usage
We want to sort the following graph.
```js
// First, we define our edges.
var graph = [
['put on your shoes', 'tie your shoes']
, ['put on your shirt', 'put on your jacket']
, ['put on your shorts', 'put on your jacket']
, ['put on your shorts', 'put on your shoes']
]
// Now, sort the vertices topologically, to reveal a legal execution order.
toposort(graph)
// [ 'put on your shirt'
// , 'put on your shorts'
// , 'put on your jacket'
// , 'put on your shoes'
// , 'tie your shoes' ]
```
(Note that there is no defined order for graph parts that are not connected
-- you could also put on your jacket after having tied your shoes...)
### Sorting dependencies
It is usually more convenient to specify *dependencies* instead of "sequences".
```js
// This time, edges represent dependencies.
var graph = [
['tie your shoes', 'put on your shoes']
, ['put on your jacket', 'put on your shirt']
, ['put on your shoes', 'put on your shorts']
, ['put on your jacket', 'put on your shorts']
]
toposort(graph)
// [ 'tie your shoes'
// , 'put on your shoes'
// , 'put on your jacket'
// , 'put on your shirt'
// , 'put on your shorts' ]
// Now, reversing the list will reveal a legal execution order.
toposort(graph).reverse()
// [ 'put on your shorts'
// , 'put on your shirt'
// , 'put on your jacket'
// , 'put on your shoes'
// , 'tie your shoes' ]
```
## API
### toposort(edges)
+ edges {Array} An array of directed edges describing a graph. An edge looks like this: `[node1, node2]` (vertices needn't be strings but can be of any type).
Returns: {Array} a list of vertices, sorted from "start" to "end"
Throws an error if there are any cycles in the graph.
### toposort.array(nodes, edges)
+ nodes {Array} An array of nodes
+ edges {Array} An array of directed edges. You don't need to mention all `nodes` here.
This is a convenience method that allows you to define nodes that may or may not be connected to any other nodes. The ordering of unconnected nodes is not defined.
Returns: {Array} a list of vertices, sorted from "start" to "end"
Throws an error if there are any cycles in the graph.
## Tests
Run the tests with `node test.js`.
## Legal
MIT License
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