# JavaScript: DHTML Quick Sort

This page demonstrates the Quick Sort algorithm. This is the most advanced algorithm of the four presented, but has some problems w.r.t. speed and the fact that it is not a 'stable' sort (see link at bottom of page for details).

To date we've found the Shell Sort algorithm to be more efficient with small-ish datasets - the kind of data displayed on websites.

id colour random
1purple946
2purple601
3orange446
4yellow426
5purple233
6green835
7green24
8green394
9blue875
10orange98
11orange690
12red57
13purple994
14yellow221
15yellow416
16green750
17orange674
18purple851
19blue665
20purple739

## 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 Quick Sort, in theory, being much faster:

``` /* global variables */ var col = 0; var parent = null; var items = new Array(); var N = 0; var quicksort = function(m, n, desc) { if(n <= m+1) return; if((n - m) == 2) { if(compare(get(n-1), get(m), desc)) exchange(n-1, m); return; } i = m + 1; j = n - 1; if(compare(get(m), get(i), desc)) exchange(i, m); if(compare(get(j), get(m), desc)) exchange(m, j); if(compare(get(m), get(i), desc)) exchange(i, m); pivot = get(m); while(true) { j--; while(compare(pivot, get(j), desc)) j--; i++; while(compare(get(i), pivot, desc)) i++; if(j <= i) break; exchange(i, j); } exchange(m, j); if((j-m) < (n-j)) { quicksort(m, j, desc); quicksort(j+1, n, desc); } else { quicksort(j+1, n, desc); quicksort(m, j, desc); } }; var sortTable = function(tableid, n, desc) { parent = document.getElementById(tableid); col = n; if(parent.nodeName == "TABLE") { parent = parent.getElementsByTagName("TBODY"); } if(parent.nodeName != "TBODY") { return false; } items = parent.getElementsByTagName("TR"); N = items.length; /* quick sort */ quicksort(0, N, desc); };```

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Th quick sort algorithm makes use of the get and compare functions presented previously in the Bubble Sort demonstration combined with the exchange function introduced in the Shell Sort demonstration for swapping non-adjacent elements.

All four methods (using OOP) are now available as external javascript files which you can find linked in the article DHTML Sorting Using OOP.

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