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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.

Working Demonstration

id colour random
1green702
2yellow143
3yellow55
4blue669
5yellow773
6orange667
7yellow769
8purple629
9yellow378
10red553
11yellow207
12yellow926
13orange587
14blue681
15blue756
16yellow24
17green966
18blue461
19red656
20green627

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")[0]; } if(parent.nodeName != "TBODY") { return false; } items = parent.getElementsByTagName("TR"); N = items.length; /* quick sort */ quicksort(0, N, desc); };

expand code box

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.

References

<JavaScript

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