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JavaScript: DHTML Shell Sort

This page demonstrates the Shell Sort algorithm which appears to be the most efficient algorithm out of the four presented on this site.

That may be due to 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.

Working Demonstration

id colour random
1green865
2green996
3red754
4blue121
5yellow9
6orange712
7red88
8orange587
9purple704
10green189
11red706
12blue223
13blue262
14yellow552
15orange334
16blue799
17purple461
18yellow754
19red576
20red237

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.

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