quicksort

问题 I'm implementing a parellel quicksort as programming practice, and after I finished, I read the Java tutorial page on Executors, which sound like they could make my code even faster. Unfortunately, I was relying on join()'s to make sure that the program doesn't continue until everything is sorted. Right now I'm using: public static void quicksort(double[] a, int left, int right) { if (right <= left) return; int i = partition(a, left, right); // threads is an AtomicInteger I'm using to make

问题 To clarify a bit on the question, I have an array and within the array are a bunch of objects. Can I rearrange the objects in the array based on the key values of each object? When I'm attempting to do so, it keeps telling me that the variable (in this case, students) is undefined. When I use the built-in sort function, it works perfectly. However, this is a school assignment and I HAVE to show the breakdown of the quicksort function. Here is the code I am using: function swap(student,

问题 I have a quicksort method that i implemented myself. i give an array of objects to that method. how do i use a comparator to tell the method which attribute the objects will be sorted by? I have googled around and found out how to implement a comparator, but not how to use it in the search method as every example ive found just used arrays.sort(). i need different getter-methods to get to the different attributes, i dont see how a comparator helps with that? i just need a little help to

问题 In Worst case Quicksort recursion Depth requires Stack space of O(n). Why it doesn't cause a stack overflow for large set in the worst case? (reversed sequence) 回答1: If you recurse on both sides of the pivot then it does cause stack overflow for sufficiently large data in the worst case. That's why nobody uses a naive QuickSort in production code. There is a simple change you can make to the algorithm to prevent Omega(n) worst-case stack use. After each partition, recursively Quicksort the

问题 After reading Stack Overflow question Using vectors for performance improvement in Haskell describing a fast in-place quicksort in Haskell, I set myself two goals: Implementing the same algorithm with a median of three to avoid bad performances on pre-sorted vectors; Making a parallel version. Here is the result (some minor pieces have been left for simplicity): import qualified Data.Vector.Unboxed.Mutable as MV import qualified Data.Vector.Generic.Mutable as GM type Vector = MV.IOVector Int

问题 After reading Stack Overflow question Using vectors for performance improvement in Haskell describing a fast in-place quicksort in Haskell, I set myself two goals: Implementing the same algorithm with a median of three to avoid bad performances on pre-sorted vectors; Making a parallel version. Here is the result (some minor pieces have been left for simplicity): import qualified Data.Vector.Unboxed.Mutable as MV import qualified Data.Vector.Generic.Mutable as GM type Vector = MV.IOVector Int

问题 I'm learning sorting algorithms and as next step, I'm trying to get my implementation perform close to the std::sort() . I'm pretty far, so far.. :-) I have 3 implementations of quicksort: standard quicksort (using temp arrays). quicksort with following optimizations: median3 used to select median tail-recursion quicksort applied only upto partition sizes < 16. For smaller partitions insertion sort is used. insertion sort applied to the whole array at once instead of applying to each

问题 I'm learning sorting algorithms and as next step, I'm trying to get my implementation perform close to the std::sort() . I'm pretty far, so far.. :-) I have 3 implementations of quicksort: standard quicksort (using temp arrays). quicksort with following optimizations: median3 used to select median tail-recursion quicksort applied only upto partition sizes < 16. For smaller partitions insertion sort is used. insertion sort applied to the whole array at once instead of applying to each

问题 i am trying to implement quicksort but i am not getting correct results. Here is my code: public static void quickSort(Comparable[] a, int start, int stop) { if (start < stop) { int pivot = partition(a, start ,stop); System.out.print("Pivot: "+a[pivot]+" Array: "); printArray(a); quickSort(a,start,pivot-1); quickSort(a,pivot+1, stop); } } public static int partition(Comparable[] a, int start, int stop) { Comparable pivot = a[stop]; int i = start; int j = stop-1; while (i < j) { while( (isLess

问题 I am trying to search for any explanation on how Quick sort works with middle element as pivot but I couldn't find any. What I am trying to look for is there any demo on how the numbers are sorted step by step because its really hard understanding the algorithms. Thanks. 回答1: The vertical bars are around the pivot: 61 11 93 74 75 21 12|55|81 19 14 86 19 79 23 44 44 11 23|19|14 21 12 19 19|11|12 14 11 19|12|14 12 |19|14 14 19 19|21|23 44 |19|21 19 21 |23|44 23 44 81 55 75|86|74 79 93 61 81 55