quicksort

When analyzing QS, every one always refers to the "almost sorted" worst case. When can such a scenario occur with natural input? The only example I came up with is re-indexing. I think people are confusing Quicksort the partition-based sorting algorithm, and "qsort" the various library implementations. I prefer to see Quicksort the algorithm as having a pluggable pivot selection algorithm, which is quite essential in analyzing its behavior. If the first element is always chosen as the pivot, then an already sorted list is the worst-case. Often there's a high probability that the array is

Java 6's Arrays.sort method uses Quicksort for arrays of primitives and merge sort for arrays of objects. I believe that most of time Quicksort is faster than merge sort and costs less memory. My experiments support that, although both algorithms are O(n log(n)). So why are different algorithms used for different types? Michael Borgwardt The most likely reason: quicksort is not stable , i.e. equal entries can change their relative position during the sort; among other things, this means that if you sort an already sorted array, it may not stay unchanged. Since primitive types have no identity

I'm working on the program just needed in the following to understand it better. What is the worst case running time for Quicksort and what may cause this worse case performance? How can we modify quicksort program to mitigate this problem? I know that it has worst case O(n^2) and I know it occurs when the pivot unique minimum or maximum element. My question is how can I modify the program to mitigate this problem. A good algorithm will be good. Quicksort's performance is dependent on your pivot selection algorithm. The most naive pivot selection algorithm is to just choose the first element

Evidently LINQ's "OrderBy" had originally been specified as unstable, but by the time of Orca it was specified as stable. Not all documentation has been updated accordingly - consider these links: Jon Skeet on OrderBy stability Troy Magennis on OrderBy stability But if LINQ's OrderBy is now "stable," then it means it is not using a quicksort (which is inherently unstable) even though some documentation (e.g. Troy's book) says it is. So my question is: if not quicksort, then what is the actual algorithm LINQ's orderBy is using? For LINQ to Objects, it's a stable quicksort that is used. For any

Haskell's website introduces a very attractive 5-line quicksort function , as seen below. quicksort [] = [] quicksort (p:xs) = (quicksort lesser) ++ [p] ++ (quicksort greater) where lesser = filter (< p) xs greater = filter (>= p) xs They also include a "True quicksort in C" . // To sort array a[] of size n: qsort(a,0,n-1) void qsort(int a[], int lo, int hi) { int h, l, p, t; if (lo < hi) { l = lo; h = hi; p = a[hi]; do { while ((l < h) && (a[l] <= p)) l = l+1; while ((h > l) && (a[h] >= p)) h = h-1; if (l < h) { t = a[l]; a[l] = a[h]; a[h] = t; } } while (l < h); a[hi] = a[l]; a[l] = p; qsort

I am totally new to python and I am trying to implement quicksort in it. Could someone please help me complete my code? I do not know how to concatenate the three arrays and printing them. def sort(array=[12,4,5,6,7,3,1,15]): less = [] equal = [] greater = [] if len(array) > 1: pivot = array[0] for x in array: if x < pivot: less.append(x) if x == pivot: equal.append(x) if x > pivot: greater.append(x) sort(less) sort(pivot) sort(greater) Brionius def sort(array=[12,4,5,6,7,3,1,15]): """Sort the array by using quicksort.""" less = [] equal = [] greater = [] if len(array) > 1: pivot = array[0]