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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	blue	734
2	yellow	489
3	purple	325
4	green	233
5	purple	160
6	yellow	402
7	orange	913
8	yellow	66
9	orange	763
10	yellow	986
11	purple	597
12	purple	571
13	orange	215
14	green	307
15	orange	659
16	orange	867
17	yellow	497
18	purple	920
19	blue	302
20	blue	817

[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.

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

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JavaScript: DHTML Shell Sort

JavaScript: DHTML Shell Sort

How does it work?

New exchange function

Related Articles - Sorting Algorithms

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