quicksort

问题 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. 回答1: 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

问题 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. 回答1: Quicksort's performance is dependent on

问题 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

问题 I was asked this question during an interview. They're both O(nlogn) and yet most people use Quicksort instead of Mergesort. Why is that? 回答1: Quicksort has O( n 2 ) worst-case runtime and O( n log n ) average case runtime. However, it’s superior to merge sort in many scenarios because many factors influence an algorithm’s runtime, and, when taking them all together, quicksort wins out. In particular, the often-quoted runtime of sorting algorithms refers to the number of comparisons or the

问题 In this code, I want to sort some random generated Numbers. If I want to sort more than ~2000 elements, Python stops working when sorting via QuickSort (after it sorted via Bubblesort) and throws "Process finished with exit code -1073741571 (0xC00000FD)". I dont know, why this problem occurs. My recursion depth is extendet, so I dont think this is the problem. Has anyone a idea, how I can solve this problem? import time import random from sys import setrecursionlimit setrecursionlimit(1000000

问题 This is my quick sort code, the partition function works well, but I got a problem while calling the recursion. The pos changes every time it starts the function and then the list limits are change as well. How to fix that? def partition(lst, start, end): pos=0 if len(lst)<2: return for i in range(len(lst[start:end])): if lst[i] < lst[end]: lst[i],lst[pos]=lst[pos],lst[i] pos+=1 elif i==(len(lst[start:end])-1): lst[end],lst[pos]=lst[pos],lst[end] return pos def quick_sort_recursive(lst, start

问题 Is it possible to implement a quicksort in Haskell (with RANDOM-PIVOT) that still has a simple Ord a => [a]->[a] signature? I'm starting to understand Monads, and, for now, I'm kind of interpreting monads as somethink like a 'command pattern', which works great for IO. So, I understand that a function that returns a random number should actually return a monadic value like IO, because, otherwise, it would break referential transparency. I also understand that there should be no way to

问题 I am attempting to take a complex number entered by a user (3-8i or -1+5i) and then sort it in ascending order in the same format as above by real number then imaginary if the same. I start by asking the user to enter a complex number or ctr-d to terminate the program and then sort. I then want to convert the string to a float. Once a float I want to quick sort it. Is this a proper way of doing this? I know I have a lot of errors. void QuickSort(vector <float> &vec) { quick_sort(vec, 0, vec

问题 Currently trying to understand how the QuickSort Algorithm operates before I implement it into code, I have the unsorted array: {7,8,2,5,1,9,3,6} In the case of this question, the right most element in the array has been picked as the pivot, 6. I have gone through the array comparing each element with 6(pivot) and depending if the array element is less than or bigger than six, done the appropriate action. As a result, now all values less than 6 are on the left and all values greater than 6

问题 I need help with this code. I need to call the quicksort method without any parameters in the main method. But this program has a parameter. How can I make it work and not have any parameter when calling it in the main method? Please help. Employee Class public class Employee { private String firstname; private int idNumber; private String lastname; Employee(String lname,String fname, int id) { lastname = lname; firstname = fname; idNumber = id; } public void setLastName(String lname)