JavaScript: DHTML Shell Sort

This page demonstrates the Shell Sort algorithm. This appears to be the most efficient algorithm out of the four presented on this site. That may be because of faults in the implementation of the Quick Sort algorithm (see related link on that page for details), but until that's confirmed you probably want to use the shell sort.

id	colour	random
1	red	139
2	orange	14
3	red	991
4	orange	202
5	purple	138
6	purple	323
7	blue	497
8	red	808
9	green	720
10	yellow	832
11	yellow	745
12	green	927
13	purple	693
14	green	232
15	yellow	191
16	blue	335
17	blue	821
18	purple	555
19	blue	163
20	green	480

[add rows to TABLE]

How does it work?

For a more detailed discussion on the sorting process, you can refer to the Bubble Sort page. The only difference between the two is the actual sorting algorithm, with the Insertion Sort, in theory, being a little bit faster:

  // global variables
  var col = 0;
  var parent = null;
  var items = new Array();
  var N = 0;

  function isort(m, k, desc)
  {
    for(var j=m+k; j < N; j+= k) {
      for(var i=j; i >= k && compare(get(i), get(i-k), desc); i-= k) {
        exchange(i, i-k);
      }
    }
  }

  function sortTable(tableid, n, desc)
  {
    parent = document.getElementById(tableid);
    col = n;

    if(parent.nodeName != "TBODY")
      parent = parent.getElementsByTagName("TBODY")[0];
    if(parent.nodeName != "TBODY")
      return false;

    items = parent.getElementsByTagName("TR");
    N = items.length;

    // shell sort
    if((k = Math.floor(N/5)) > 7) {
      for(var m=0; m < k; m++) isort(m, k, desc);
    }

    if((k = Math.floor(N/7)) > 7) {
      for(var m=0; m < k; m++) isort(m, k, desc);
    }

    for(k=7; k > 0; k -= 2) {
      for(var m=0; m < k; m++) isort(m, k, desc);
    }
  }

Interestingly, the Shell Sort algorithm actually makes use of the previously presented Insertion Sort algorithm.

New exchange function

Because the Shell Sort algorithm requires non-adjacent items to be swapped, we need to make some changes to the exchange function that was previously used for both the Bubble Sort and Insertion Sort. The get and compare functions remain unchanged.

  function exchange(i, j)
  {
    if(i == j+1) {
      parent.insertBefore(items[i], items[j]);
    } else if(j == i+1) {
      parent.insertBefore(items[j], items[i]);
    } else {
      var tmpNode = parent.replaceChild(items[i], items[j]);
      if(typeof(items[i]) == "undefined") {
        parent.appendChild(tmpNode);
      } else {
        parent.insertBefore(tmpNode, items[i]);
      }
    }
  }

For an even more advanced sorting technique, see the Quick Sort demonstration.

JavaScript DHTML Insertion Sort
JavaScript DHTML Sorting Using OOP
JavaScript DHTML Sorting Using OOP - Example 1
JavaScript DHTML Shell Sort
JavaScript DHTML Quick Sort
JavaScript DHTML Bubble Sort
PHP Sorting Arrays of Arrays
PHP Sorting SimpleXMLElement Object arrays

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JavaScript: DHTML Shell Sort

JavaScript: DHTML Shell Sort

How does it work?

New exchange function

Related Articles - Sorting Algorithms