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    <p>Check wikipedia, there is a little example with a bit smaller list of inplace quicksort <a href="http://en.wikipedia.org/wiki/Quicksort" rel="nofollow">http://en.wikipedia.org/wiki/Quicksort</a></p> <p>With your example the idea is to partition</p> <pre><code>{15, 19, 34, 41, 27, 13, 9, 11, 44} </code></pre> <p>into</p> <pre><code>{13, 9, 11 -- 15 -- 19, 34, 41, 27, 44} </code></pre> <p>So first we move pivot to the end</p> <pre><code>Swap 44, and 15 {44, 19, 34, 41, 27, 13, 9, 11, 15} ^ ^ Than check 44, its larger than pivot, so swap with one one before last... {11, 19, 34, 41, 27, 13, 9, 44, 15} ^ ^ than check element at some position as last one was larger than pivot. 9 &lt; 15, so proceed to the next, 19 &gt; 15 =&gt; swap {11, 9, 34, 41, 27, 13, 19, 44, 15} ^ ^ swap again {11, 9, 13, 41, 27, 34, 19, 44, 15} ^ ^ next {11, 9, 13, 41, 27, 34, 19, 44, 15} ^ ^ and second last swap {11, 9, 13, 27, 41, 34, 19, 44, 15} ^ Now as forward and backward indices reached each other, we swap pivot into right position {11, 9, 13, 15, 41, 34, 19, 44, 27} </code></pre> <p>And we got partitioned set. Items less than 15 at the beginning, than pivot = 15, and then greater elements.</p> <p>EDIT: algorithm described in wikipedia article is a bit different:</p> <pre><code>Legend: ^ = storeindex # = i {44, 19, 34, 41, 27, 13, 9, 11, 15} ^# {44, 19, 34, 41, 27, 13, 9, 11, 15} ^ # ... until ... {44, 19, 34, 41, 27, 13, 9, 11, 15} ^ # {13, 19, 34, 41, 27, 44, 9, 11, 15} ^ # {13, 9, 34, 41, 27, 44, 19, 11, 15} ^ # {13, 9, 11, 41, 27, 44, 19, 34, 15} ^ # {13, 9, 11, 15, 27, 44, 19, 34, 41} ^- pivot </code></pre>
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    1. POQuicksort with first element as pivot example
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    1. POQuicksort with first element as pivot example
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    1. COafter that you would proceed recursively applying quicksort on the {13, 9, 11} and {27, 44, 19, 34, 41} part of the arrays. Try to experiment with eg. a deck of cards how it would work!
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    2. COThis helped a lot, thank you for clearing up my confusion!
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