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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
1yellow226
2green911
3blue350
4blue31
5orange710
6yellow12
7orange583
8red809
9red842
10blue64
11yellow408
12yellow605
13red258
14blue279
15red513
16blue655
17yellow485
18orange769
19purple177
20yellow839
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); }

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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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