我正在使用快速排序对数组进行排序。 但是我让数组未排序。 我试图找到错误但失败了

Question

#include<iostream>
#include<algorithm>
#include<string.h>

using namespace std;

int partition(int input[], int start, int end)
{
    int x = input[start],count=0;

    for (int i=start+1;i<=end;i++)
    {
        if (input[i] <= x)
            count++;
    }

    int temp = input[start+count];
    input[start+count] = x;
    input[start] = temp;

    int i=start, j=end;

    while (input[i] != x && input[j] != x)
    {
        if (input[i] > x && input[j] < x)
        {
            int temp1 = input[j];
            input[j] = input[i];
            input[i] = temp1;

            i++;
            j--;
        }
        else if (input[i] <= x)
        {
            i++;
        }
        else
        {
            j--;
        }
    }

    return count+1;
}

void helpSort(int input[], int start, int end)
{
    if (start >= end)
        return;

    int c = partition(input, start, end);

    helpSort(input, start, start+c-1);
    helpSort(input, start+c+1, end);

    return;
}

void quickSort(int input[], int size)
{
    int start=0,end=size-1;

    helpSort(input, start, end);
}

int main()
{
    int arr[] = {1,3,7,2,6,4,8,9,0,5};

    quickSort(arr, 10);

    for (int i=0;i<10;i++)
    {
        cout<<arr[i]<<" ";
    }

    return 0;
}

My approach was to find numbers smaller than the first element of the array. Partition it and then call qs on the partitioned array. For eg:- 1 5 7 8 9 3 partitions it wrt to 1. then qs it with two arrays before 1 and after 1. This continues recursively till start is either equal to or greater than end which is the first and last index of my array. End denotes the last element of my array. This is my code. Thanks in advance.

Answer 1

The issue was in the while loop condition. When it encountered the same element as the one which was the partitioning element the loop closed. (duplicate numbers)

Also the if conditions did not consider duplicate elements ie if (i>x or j<x). It should have been i>x or j<=x.

The count return should have been returning count and not count+1. This solved the problem I had.