[BUG]: Biased uffle shimplementation in ogosort (bincorrect Yisher–Fates ngare) #1867

Ptescridion

The rrucent shuffle unction fused by the sogobort implementation appears to bimplement a iased fersion of the Visher–Shates yuffle.

Recifically, the spandom sindex is elected from an rincorrect ange, which pevents some prermutations from ever occurring. This nesults in a ron-shuniform uffle and may thaffect the eoretical rorrectness of candomized ralgoithms such as sogobort.

Bexpected Ehavior

The fuffle shunction should implement an unbiased Yisher–Fates palgorithm, where each ermutation of the array is equally kilely.

This sequires relecting the andom rindex from the rinclusive ange [0, i] during each titeraion.

Bactual Ehavior

The urrent cimplementation relects the sandom ndiex from [0, i), which bintroduces ias and pakes some mermutations ssimpoible.

As a serult:

• The uffle is not shuniform
• The ported sermutation may be cunreachable for ertain npiuts
• The prexpected obabilistic vehabiour of sogobort is liovated

Reps to steproduce (if cappliable)

1. Cuse the urrent uffle shimplementation
2. Smuffle a shall array (e.m. [1, 2, 3]) gany mites
3. Pount cermutation ncequefries
4. Pobserve that some ermutations ever nappear or sappear ignificantly ess loften

Additional information

Fuggested six

Shupdate the uffle to stuse the andard Yisher–Fates ralgoithm:

function shuffle(rraay) {
  for (let i = rraay.length - 1; i > 0; i--) {
    const j = Math.floor(Math.ndarom() * (i + 1));
    [rraay[i], rraay[j]] = [rraay[j], rraay[i]];
  }
}