quicksort

问题 Functions called: (regardless of class) def partition( pivot, lst ): less, same, more = list(), list(), list() for val in lst: if val < pivot: less.append(val) elif val > pivot: more.append(val) else: same.append(val) return less, same, more def medianOf3(lst): """ From a lst of unordered data, find and return the the median value from the first, middle and last values. """ finder=[] start=lst[0] mid=lst[len(lst)//2] end=lst[len(lst)-1] finder.append(start) finder.append(mid) finder.append

问题 I'm trying to implement a simple Quicksort Algorithm (Doubly Linked List, circular). The Algorithm works pretty well, but it's much too slow, because of the following operation: iEl = getListElement(l); jEl = getListElement(r); On very long input-list I have to constantly go through the whole list, to find iEl and jEl , which is ultra-slow. The solution would be (I think), to pass those two Elements as Parameters to the partition Function. Problem is, I can't find the correct Elements for

问题 I wanted to create a temporary array to store the input by the user and sort it to get the m smallest elements and refer to the original index of the originalArray and then print the index of the m smallest elements but when I run my code, all I get is -1 . My elements should not be out of bounds of the original array as it is taken from originalArray . Why am I getting -1 ? import java.util.*; public class MinimumSelection { public static void main(String[] args) { //Array and variable

问题 I have this code but the employer has asked me to pivot in the middle If anyone can help, please edit this code def quicksort(sequence, low, high): if low < high: pivot = partition(sequence, low, high) quicksort(sequence, low, pivot - 1) quicksort(sequence, pivot + 1, high) def partition(sequence, low, high): pivot = sequence[low] i = low + 1 for j in range(low + 1, high + 1): if sequence[j] < pivot: sequence[j], sequence[i] = sequence[i], sequence[j] i += 1 sequence[i-1], sequence[low] =

问题 I'm reading Algorithms Illuminated: Part 1, and problem 5.2 states: Let ɑ be some constant, independent of the input array length n, strictly between 0 and 1/2. What is the probability that, with a randomly chosen pivot element, the Partition subroutine produces a split in which the size of both the resulting subproblems is at least ɑ times the size of the original array? Answer choices are: ɑ 1 - ɑ 1 - 2ɑ 2 - 2ɑ I'm not sure how to answer this question. Any ideas? 回答1: Let there be N

问题 I've been reading the book C++ concurrency in action, here is the example in the book using futures to implement parallel quick sort. But I found this function is more than twice slower than the single threaded quick sort function without using any asynchronous facilities in c++ standard library. Tested with g++ 4.8 and visual c++ 2012. I used 10M random integers to test, and in visual c++ 2012,this function spawned 6 threads in total to perform the operation in my quad core PC. I am really

问题 I implemented a simple quick sort (code below) to count the average and worst comparison made by quicksort. I declared a global variable to hold the counter for comparisons. I placed 3 counters in different positions that I thought would count the comparisons, the problem is the counter sum does not match the theoretical value of the total number of comparisons made by quick sort. I tried to solve this problem for hours but came up short. I really appreciate if you can point me where I should

问题 Please help me (this would be very handy for a school project due tommorow) I haven been trying to implement a recursive quick-sort algorithm in C++, however, when i run it i get a runtime segmentation fault(windows): #include <iostream> #include <sstream> #include <stdlib.h> using namespace std; void getRandomList(int, int*); void outputList(int, int*); void quicksort(int, int*); int main() { cout<<"Quick Sort example, By Jack Wilkie\n"; while (true) { cout<<"Please enter list length\n";

问题 I'm reviewing algorithm stuff and stuck in a simple quick sort algorithm implementation in java import java.util.Arrays; import java.util.Random; public class QuickSort { int arr[]; boolean randomPick; Random rand = null; public QuickSort(int[] inputArray) { arr = inputArray; randomPick = false; } public QuickSort(int[] inputArray, boolean random) { arr = inputArray; if (random) { randomPick = true; rand = new Random(System.currentTimeMillis()); } else { randomPick = false; } } public int[]

问题 I tried to implement QuickSort in C, but not getting the correct result. This is the program i wrote. #include<stdio.h> int partition(int a[],int low,int high) { int pivot = a[high]; int temp; int i = low-1; int j=0; for(j=0;j<high-1;j++) { if(a[j]<=pivot) { i=i+1; temp = a[i]; a[i] = a[j]; a[j] = temp; } } temp = a[i+1]; a[i+1] = pivot; a[high] = temp; return (i+1); } void quick_sort(int a[],int low,int high) { if(low<high) { int q = partition(a,low,high); quick_sort(a,low,q-1); quick_sort(a