Visualization of Quick sort





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Uploaded on Feb 21, 2009

See a new version of this video: http://www.youtube.com/watch?v=aXXWXz... (HD + narration)

A demonstration of the Quick Sort sorting algorithm.

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It demonstrates two comparison sorting algorithms: Bubble sort and Quick sort.
Comparison sorting algorithms are only allowed to 'see' the data through a sequence of pair-wise comparisons, therefore they are applicable to any type of comparable objects: numbers, strings, colored balls, etc

Bubble sort is very simple but has poor performance. A comparison sorting algorithm's performance is usually measured by the number of comparisons it makes. Bubble sort performs on the order of n^2 comparisons to sort n elements.

Quick sort is only slightly more complicated but usually performs much better (as demonstrated in the video). It performs on average an order of n log(n) comparisons to sort n elements. This is much lower than n^2 for large values of n. However, if the algorithm makes some 'unlucky' choices it might require n^2 comparisons after all.

Other algorithms exist that guarantee the number of comparisons will not exceed n log(n), however, in practice Quick sort usually out-performs all other comparison sorting algorithms due to its simplicity.

If other operations other than pair-wise comparisons are allowed, then a broader range of algorithms can be used. Some of them can perform much faster than Quick sort, but they are limited to a particular type of elements, e.g., numbers is a certain range.


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