quickselect

QuickSelect Algorithm Understanding

由 走远了吗. 提交于 2019-12-17 15:33:10
问题 I've been poring over various tutorials and articles that discuss quicksort and quickselect, however my understanding of them is still shaky. Given this code structure, I need to be able to grasp and explain how quickselect works. // return the kth smallest item int quickSelect(int items[], int first, int last, int k) { int pivot = partition(items, first, last); if (k < pivot-first) { return quickSelect(items, first, pivot, k); } else if (k > pivot) { return quickSelect(items, pivot+1, last,

Quick Select Algorithm

由 空扰寡人 提交于 2019-12-13 21:04:35
问题 Im trying to implement the Quick Select Algorithm on a Array that has randomly generated numbers. Now after writing the algorithm in code, it does not sort the array from lowest to highest nor am i able to find the kth smallest element. I would appreciate the help i get. Thank you. #include<iostream> #include<ctime> #include<cstdlib> using namespace std; void printArray(int *myArray, int n){ for(int i = 0; i < n; i++){ cout << myArray[i] << " "; } } int Partition(int *myArray, int

Python based quickselect Implementation resulting in error

由 北城余情 提交于 2019-12-11 15:12:57
问题 I have small python code that implements the quickselect discussed here. import random def Quickselect(A, k): if not A: return pivot = random.choice(A) i = 0 A1 = [] A2 = [] # Two new arrays A1, A2 to store the split lists for i in range(len(A)): if A[i] < pivot : A1.append(A[i]) else: A2.append(A[i]) if k < len(A1): return Quickselect(A1, k) if k > len(A) - len(A2): return Quickselect(A2, k-(len(A) - len(A2))) else: return pivot pass def main(): A = [45,1,27,56,12,56,88] print(Quickselect(A

QuickSelect Algorithm Understanding

由 六眼飞鱼酱① 提交于 2019-11-27 18:47:02
I've been poring over various tutorials and articles that discuss quicksort and quickselect, however my understanding of them is still shaky. Given this code structure, I need to be able to grasp and explain how quickselect works. // return the kth smallest item int quickSelect(int items[], int first, int last, int k) { int pivot = partition(items, first, last); if (k < pivot-first) { return quickSelect(items, first, pivot, k); } else if (k > pivot) { return quickSelect(items, pivot+1, last, k-pivot); } else { return items[k]; } } I need a little help with breaking down into pseudo-code, and
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