计算快速排序比较 [英] counting quicksort comparisions

问题描述

嘿

i我仍然是编程的初学者，但我正在尝试编写一个计算快速排序计划中比较次数的程序





这是我的代码

hey
i am still a beginner at programming but i am trying to write a program that counts the number of comparisons in a quicksort program


this is my code

package algo_quicksort;

public class Algo_quicksort {

    public static int partition(int[]A,int p,int r){
        int x=A[p];
        int i=p+1;
        int temp;
        for(int j=p+1;j<r;j++){
            if(A[j]<x){//if A[j] is bigger than the pivot do nothing 
                temp=A[j];
                A[j]=A[i];
                A[i]=temp;
                i++;
            }
        }
        temp=A[p];
        A[p]=A[i-1];
        A[i-1]=temp;
        return i-1;
    }
    public static long quickSort(int[]A,int startPos,int length){
        if(length==1){
            return 0;
        }
        else{
            if(startPos<length){
            int pivot= partition(A,0,length);
          quickSort(A,startPos,pivot+1);
          quickSort(A, pivot+2,length); 
            return length-startPos-1;
        }
            else{
                return 0;
            }
    }
    }
    
    
    public static void main(String[] args) {
        int a[]={3,2,4};
        System.out.println("# of comparisons is: " +quickSort(a,0,a.length));

        System.out.println("A[] after quicksort is: ");
        
        for(int i=0;i<a.length;i++){
            System.out.print(a[i]+"  ");
        }

    }
}

它适用于任何大小的数组3或更少

但如果它比任何更大它在递归调用时给我一个stackoverflow异常

i尝试调试我的代码但是无法弄清楚它出错的地方

i会感激我得到的任何帮助^ _ ^

it works perfectly for any array of size 3 or less
but if it is any bigger than that it gives me a stackoverflow exception at the recursive call
i tried debugging my code but could not figure out where it's going wrong
i would appreciate any help i get ^_^

推荐答案

你的快速排序在很多地方都是错误的。你为什么不复制别人的快速实施方案： http://www.algolist.net/Algorithms/Sorting/Quicksort [ ^ ]

Your quicksort is simply buggy in many places. Why don't you copy someone else' quicksort implementation: http://www.algolist.net/Algorithms/Sorting/Quicksort[^]

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