shell-sort.js

/*
 * CODE: http://blog.benoitvallon.com/sorting-algorithms-in-javascript/sorting-algorithms-in-javascript-all-the-code/#shell-sort
 *
 * Shell sort is an in-place comparison sort which can be seen as either a
 generalization of sorting by exchange (bubble sort) or sorting by insertion (
 insertion sort). The method starts by sorting pairs of elements far apart 
 from each other, then progressively reducing the gap between elements to be 
 compared. Starting with far apart elements can move some out-of-place 
 elements into position faster than a simple nearest neighbor exchange.
 *
 * MORE INFO: https://en.wikipedia.org/wiki/Shellsort
 */
export function shellSort(arr) {
  const len = arr.length;
  for (let h = len; h > 0; h = parseInt(h / 2)) {
    for (let i = h; i < len; i++) {
      let k = arr[i];
      let j = i;
      for (; j >= h && k < arr[j - h]; j -= h) {
        arr[j] = arr[j - h];
      }
      arr[j] = k;
    }
  }
  return arr;
}