The mission is an idea of przemyslaw.daniel .

Let’s imagine a list of all the permutations of a given set. Every item on the list has it’s index (starting from 1). The task is to calculate the permutation index.

You are given a tuple of integers. It represents one of the permutations of the consecutive integers (starting from 0). You have to return the permutation index of the tuple.

**
For example
**

- Input: (1, 2, 0)
- All the consecutive permutations are:
- (0, 1, 2)
- (0, 2, 1)
- (1, 0, 2)
- (1, 2, 0) !!!
- (2, 0, 1)
- (2, 1, 0)
- Output: 4

**
Example:
**

assert permutation_index((2, 0, 1)) == 5 assert permutation_index((2, 1, 3, 0, 4, 5)) == 271

**
Input:
**
One of the permutations of the consecutive integers (a tuple of integers).

**
Output:
**
The permutation index (an integer).

**
Precondition:
**

- sorted(input) == list(range(len(input)))

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=

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.