quicksort | 易学教程

How to implement quicksort using recursion

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问题 I am practicing using recursion to implement the quicksort algorithm. I am getting the error: RecursionError: maximum recursion depth exceeded in comparison Here is the error: In [2]: run quicksort.py --------------------------------------------------------------------------- RecursionError Traceback (most recent call last) ~/Desktop/algo/quicksort.py in <module>() 27 28 test = QuickSort() ---> 29 print(test.partition([7, 2, 1, 8, 6, 3, 5, 4], 0, 7)) ~/Desktop/algo/quicksort.py in partition

quicksort an array and do binary search in java

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问题 So I have to make a method which is using the quicksort as a sort algorithm without using the Java API. Then I have to write another method that gives the sorted array back and using the binary search return true if the searched element is found in it. I have no idea where am I making the stupid mistake. public class Aufgabe1 { public static void sort(int[] array) { /* TODO: add code here */ sort(array, 0, array.length - 1); } public static void sort(int[] array, int start, int end) { int i =

How can I optimize parallel sorting to improve temporal performance?

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问题 I have an algorithm for parallel sorting a list of a given length: import Control.Parallel (par, pseq) import Data.Time.Clock (diffUTCTime, getCurrentTime) import System.Environment (getArgs) import System.Random (StdGen, getStdGen, randoms) parSort :: (Ord a) => [a] -> [a] parSort (x:xs) = force greater `par` (force lesser `pseq` (lesser ++ x:greater)) where lesser = parSort [y | y <- xs, y < x] greater = parSort [y | y <- xs, y >= x] parSort _ = [] sort :: (Ord a) => [a] -> [a] sort (x:xs)

Efficient string sorting algorithm

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问题 Sorting strings by comparisons (e.g. standard QuickSort + strcmp-like function) may be a bit slow, especially for long strings sharing a common prefix (the comparison function takes O(s) time, where s is the length of string), thus a standard solution has the complexity of O(s * nlog n). Are there any known faster algorithms? 回答1: If you know that the string consist only of certain characters (which is almost always the case), you can use a variant of BucketSort or RadixSort. 回答2: You could

Efficient string sorting algorithm

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Another Quicksort stackoverflow

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问题 So I've been trying to implement a quicksort myself, just to learn something from it, but it also generates a stackoverflowexception, but I can't seem to find what the cause is. Can someone give me a clue? public void Partition(List<int> valuelist, out List<int> greater, out List<int> lesser) { lesser = new List<int>(); // <-- Stackoverflow exception here! greater = new List<int>(); if (valuelist.Count <= 1) return; pivot = valuelist.First(); foreach (int Element in valuelist) { if (Element <

Quick Sort Time Complexity Best Case Input

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问题 I have to find time complexity of quick sort for BEST CASE INPUT in a c program & i have selected the last element of array as pivot. Now i know what input values i have to enter for best case, i.e., keep 1st middle element at the last place(pivot) & next pivot should be the next middle element. But i have to generate this kind of best case input array of very big sizes like 1000, 5000, 100000.., for quick sort. I can code, but can anyone please help me understand how to generate that kind of

Calculate Execution Times in Sort algorithm

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问题 I implemented Merge Sort and Quick Sort in C++, and I wanna get the execution times using each of two with many of cases those are already Sorted or not & has different size. #include <iostream> #include <ctime> #include <vector> #include <algorithm> using namespace std; void Merge(vector<int>& s, int low, int mid, int high) { int i = low; int j = mid + 1; int k = low; vector<int> u(s); while (i <= mid && j <= high) { if (s.at(i) < s.at(j)) { u.at(k) = s.at(i); i++; } else { u.at(k) = s.at(j)

Calculate Execution Times in Sort algorithm

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快速排序 quicksort

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快速排序是一种最常见的高效排序算法，时间复杂度为 O ( n 2 ) ，但是平均的时间复杂度是 O(n·lgn) 。而且可以证明，随机选取参照值的快速排序的时间复杂度期望值为 O(n·lgn) 。 C语言中已经存在快速排序的函数qsort: #include <stdlib.h> void qsort(void *base, size_t nmemb, size_t size, int(*compar)(const void *, const void *)); 本文仿照该函数的结构，提供了随机化快速排序的一种实现，还包括了两个可以作为函数指针参数的比较函数，分别是整形比较函数comparInt和字符串比较函数comparStr。 #include <stdio.h> #include <string.h> #include <stdlib.h> void *quicksort(void *base, size_t nmeb, size_t size, int(*compar)(const void *, const void *)) { if (nmeb < 2) return; int i, j, key; key = rand() % nmeb; swap(base, base + key * size, size); i = 1; j = nmeb - 1; while