Post History

Shuffle a subset of a list [FINALIZED]

[Posted](https://codegolf.codidact.com/posts/282497)

<sup>Idea shamelessly stolen from [caird](https://chat.stackexchange.com/transcript/message/58238435#58238435) and [rak1507](https://chat.stackexchange.com/transcript/message/58238593#58238593)</sup>

Shuffle a subset of a list of unique, positive integers with uniform randomness, given the indices of that subset. For example, given the list \$[A, B, C, D, E, F, G, H]\$ and the indices \$[0, 3, 4, 5, 7]\$ (0-indexed), you would extract the list \$[A, D, E, F, H]\$, shuffle it, and insert the shuffled elements back according to the list of indices. Some possible results of this are (elements that stayed in place are bolded)
$$[H, \textbf{B}, \textbf{C}, D, A, E, \textbf{G}, F]$$
$$[A, \textbf{B}, \textbf{C}, D, E, F, \textbf{G}, H]$$
$$[F, \textbf{B}, \textbf{C}, E, A, H, \textbf{G}, D]$$.

## Rules

- Every possible rearrangement of the list should have a non-zero chance of being chosen.
- You may use zero- or one-indexing, but please specify which you use.
- The indices in the input are guaranteed to be unique and valid.
- This is [tag:code-golf], so least number of bytes wins.


## Test cases

All of these examples use 0-indexing.
```
List
Indices
Possible output

[1,2,3,4,5,6,7]
[0,1,2,3,4,5,6]
[2,3,6,1,0,4,5], etc.

[1,2,3,4,5,6,7]
[0,2,4,6]
[3,2,7,4,5,6,1], etc.

[93,6,10,1,200,41,78,31,34,27]
[0,3,4,8,9]
[1,6,10,27,93,41,78,31,200,34], etc.
```

## Questions for Meta:
- How do I enforce randomness?
- Is this a dupe?
- Is this uninteresting?

Shuffle a contiguous subset of a list

Note: I had modified this to use a *contiguous* subset, but am now making it any subset, so this draft will be changed later, I'm just too lazy to make the changes right now.

<sup>Idea shamelessly stolen from [caird](https://chat.stackexchange.com/transcript/message/58238435#58238435) and [rak1507](https://chat.stackexchange.com/transcript/message/58238593#58238593)</sup>

Shuffle a subset of a list of unique, positive integers randomly, given the start and end indices of that subset. For example, given the list \$[A, B, C, D, E, F, G, H]\$ and the indices 0 and 5 (0-indexed, with an exclusive end), you would extract the sublist \$[A, B, C, D]\$, shuffle it, and insert it back. Some possible results are \$[D, C, B, A, E, F, G, H]\$, \$[D, B, A, C, E, F, G, H]\$, and \$[A, C, B, D, E, F, G, H]\$.

## Rules

- Every possible rearrangement of the list should have a non-zero chance of being chosen.
- You may use zero- or one-indexing, but please specify which you use.
- You may also choose if the end indices are inclusive or exclusive.
- If the end index is exclusive, the start index is guaranteed to be less than the end index. Otherwise, the start index is guaranteed to be less than or equal to the end index (an empty subset). Both indices are also guaranteed to be within the bounds of the list.
- This is [tag:code-golf], so least number of bytes wins.

## Test cases

All of these use zero-indexing, and the end indices are exclusive.
```
List
Start,end
Possible output

[1,2,3,4,5]
2,4
[1,2,4,3,5]

[1,2,3,4,5]
[2,2]
[1,2,3,4,5] (only possible output)
```

## Questions for Meta:
- How do I enforce randomness?
- Is this a dupe?
- Is this uninteresting?