@jscad/modeling/src/operations/extrusions/earcut/linkedListSort.js

Constructive Solid Geometry (CSG) Library for JSCAD

// Simon Tatham's linked list merge sort algorithm
// https://www.chiark.greenend.org.uk/~sgtatham/algorithms/listsort.html
const sortLinked = (list, fn) => {
  let i, p, q, e, numMerges
  let inSize = 1

  do {
    p = list
    list = null
    let tail = null
    numMerges = 0

    while (p) {
      numMerges++
      q = p
      let pSize = 0
      for (i = 0; i < inSize; i++) {
        pSize++
        q = q.nextZ
        if (!q) break
      }

      let qSize = inSize

      while (pSize > 0 || (qSize > 0 && q)) {
        if (pSize !== 0 && (qSize === 0 || !q || fn(p) <= fn(q))) {
          e = p
          p = p.nextZ
          pSize--
        } else {
          e = q
          q = q.nextZ
          qSize--
        }

        if (tail) tail.nextZ = e
        else list = e

        e.prevZ = tail
        tail = e
      }

      p = q
    }

    tail.nextZ = null
    inSize *= 2
  } while (numMerges > 1)

  return list
}

module.exports = sortLinked