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JavaScript: DHTML Quick Sort

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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). At this stage we've found the Shell Sort algorithm to be more efficient with web data.

idcolourrandom
1purple325
2yellow743
3purple619
4green778
5orange704
6yellow413
7red688
8yellow245
9red72
10purple893
11blue438
12purple954
13orange155
14purple843
15yellow963
16yellow345
17green29
18orange942
19red703
20orange726
Sort by DESC?

[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 Quick Sort, in theory, being much faster:

// global variables var col = 0; var parent = null; var items = new Array(); var N = 0; function quicksort(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); } } 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; // quick sort quicksort(0, N, desc); }

expand code box

This algorithm makes use of the get and compare function presented previously in the Bubble Sort demonstration, and the exchange function introduced in the Shell Sort demonstration.

The sorting functions presented so far have all been quite inefficient because they first have to read the DOM and then apply the various algorithms. To get around this limitation, each of the sorting algorithms has also been implemented using object-oriented (OOP) techniques.

All four methods (using OOP) are now available as external javascript files on the related page: DHTML Sorting Using OOP.

References

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