feat(challenges): add offset-arrays

challenges/offset-arrays/README.md

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+# offset-arrays
+
+Created by [@Divlo](https://github.com/Divlo) on 29 June 2021.
+
+## Instructions
+
+### Goal
+
+To settle the debate of 0-based vs 1-based indexing I have created a language where you must explicitly state the range of indices an array should have.
+
+For example, given an array definition "A[-1..1] = 1 2 3", you would have:
+
+- A[-1] = 1
+- A[0] = 2
+- A[1] = 3
+
+You are given a list of `n` array definitions and your job is to figure out what number is found in a given index `i` of an array `arr`. Note that the indexing operations may be nested (in the above example, A[A[-1]] would produce result 3).
+
+### Input
+
+- **Line 1:** An integer `n` for the number of array assignments
+- **`N` next lines:** One array assignment per line: `array_identifier` [ `first_index` .. `last_index` ] = `last_index - first_index + 1` integers separated by space
+- **Line `n+2`:** Element to print: `arr` [ `i` ]
+
+### Constraints
+
+- 1 <= `n` <= 100
+- Array names consist only of uppercase letters A to Z
+- Array lengths are between 1 and 100 (no empty arrays)
+- Indexing operations have at most 50 levels of nesting
+- Indices are always within bounds in the test cases
+
+## Source
+
+- [CodinGame](https://www.codingame.com/ide/puzzle/offset-arrays)
+
+## Examples
+
+See the `test` folder for examples of input/output.
+
+### Example 1
+
+#### Input
+
+```txt
+3
+A[-1..1] = 1 2 3
+B[3..7] = 3 4 5 6 7
+C[-2..1] = 1 2 3 4
+A[0]
+```
+
+#### Output
+
+```txt
+2
+```