/*
 * Shell Sort sorts an array based on  insertion sort algorithm
 * more information: https://en.wikipedia.org/wiki/Shellsort
 *
 */
function shellSort(items) {

    var interval = 1;

    while (interval < items.length / 3) {

        interval = interval * 3 + 1;
    }

    while (interval > 0) {

        for (var outer = interval; outer < items.length; outer++) {

            var value = items[outer];
            var inner = outer;

            while (inner > interval - 1 && items[inner - interval] >= value) {
                items[inner] = items[inner - interval];
                inner = inner - interval;
            }
            items[inner] = value;
        }
        interval = (interval - 1) / 3;
    }
    return items;
}

//Implementation of shellSort

var ar = [5, 6, 7, 8, 1, 2, 12, 14];
//Array before Sort
console.log(ar);
shellSort(ar);
//Array after sort
console.log(ar);