Question

Can anyone point out why this implementation of quick sort is not working, i have gone through it several times and can’t seem to find the error

int quickPartition ( int data[], int p, int r)
{
    int x=data[r];
    int i=p-1;
    for (int j=p; j<r; j++)
    {
        if(data[j]<x)
        {
            i++;
            int temp=data[i];
            data[i]=data[j];
            data[j]=temp;
        }
        int temp=data[i+1];
        data[i+1]=data[r];
        data[r]=temp;   
    }
    i++;
    cout<<"i:"<<i<<endl;
    return i;
}

void myQuickSort(int data[], int left, int right)
{       
    if(left<right)
    {
        int q=quickPartition(data,left,right);
        myQuickSort(data,left,q-1);
        myQuickSort(data,q+1,right);
    }
}

the call to quicksort is simply

myQuickSort(anArray,0,size-1);

Answer 1

Methinks

    int temp=data[i+1];
    data[i+1]=data[r];
    data[r]=temp;

should go outside the for loop.