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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
1red300
2blue213
3yellow324
4yellow170
5blue725
6blue9
7purple990
8orange584
9orange471
10yellow670
11purple536
12red47
13purple806
14green517
15green623
16green21
17green964
18red38
19orange837
20red722

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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