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POQuicksort not working
 

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  1. POQuicksort not working
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    <p>This is all my code for my quicksort method, it works on a set of 21 numbers, but not on my real data set, which is about 100000. I have no idea what is wrong, I've been fiddling for two hours and it is due soon! Any help would be very welcome</p> <pre><code>public static void hybridQuicksort( int[] a, int start, int end ) { final int MIN = 13; if ( end - start &gt;= MIN ) { int pivot = findPivot( a, start, end ); pivot = partition ( a, start, end, pivot ); hybridQuicksort( a, start, pivot - 1 ); hybridQuicksort( a, pivot + 1, end); } else { insertionSort( a, start, end ); } } //partitions the array based on the pivot public static int partition( int[] a, int start, int end, int pivot ) { int up = start + 1; int down = end; while ( up &lt;= down ) { while ( a[up] &lt;= pivot) up++; while ( a[down] &gt; pivot) down--; if ( up &lt;= down ) swap( a, up, down ); } swap( a, start, down ); return up; } //finds the first, middle, middle of first and middle, middle of middle and last //and last numbers and sets their median as the pivot public static int findPivot( int[] a, int start, int end ) { //swap the 4 numbers to the start of the array, leaving the first as is swap( a, start + 1, end - 1 ); swap( a, start + 2, (start + end) / 2); swap( a, start + 3, end / 4); swap( a, start + 4, (end / 2) + (end / 4) ); //sort the 5 numbers insertionSort( a, 0, 5 ); //swap the median to the front, that's the pivot swap( a, start, start + 2 ); //return the pivot return a[start]; } </code></pre>
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    1. COThis is not really a place for solving homework questions; especially ones that are nearly due. Perhaps you should ask a class mate or look over some of the qsort tutorials online.
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      1. USRobert Massaioli
    2. COIf you will look at the code, you will notice it is complete, so no one is 'solving' my homework problem. I've done nearly all of it, there is just some glitch in there that I can't seem to find so I was hoping someone would take a glance and see if they can find it. Is that wrong?
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    3. COActually, I take what I said back; while the median of 5 insert sort was/is still wrong, that it was a partitioning problem isn't it (I lost sight of bits of code); lexu is right though.
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      1. USCoderTao
 

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