Question

Use QUICKSORT, sort the integer array contains even number in ascending order and uneven number in descending order.

ex: input int a[8]={4,6,1,2,5,3,8,7}
=>output is {2,4,6,8,7,5,3,1}.

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I think the QSort function will give me look like this B={4,6,2,8,1,3,7,5} and i’ll split B array to two array is C and D.

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C array contains even number {4,6,2,8} and i’ll use QuickSort to sort C array like this {2,4,6,8}

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D array contains uven number {5,3,1,7} and i’ll use QuickSort to sort D array like this {7,5,3,1}
After that i’ll plus C and D. Finally my expected result is {2,4,6,8,7,5,3,1}
and this is my code :(! Thanks alot!

    void Input(int a[], int n)
    {
        for(int i = 0; i<n;i++)
        {
            cout<<"a["<<i<<"]: ";
                cin>>a[i];
        }
    }
    void Display(int a[],int n)
    {
        for(int i = 0;i < n; i++)
        {
            cout<<a[i]<<" ";
        }
        cout<<endl;
    }
    void Swap(int &a, int &b)
    {
        int temp = a;
        a=b;
        b=temp;
    }
    void QuickSort(int a[],int Left ,int Right)
    {
        int i, j, x;
        x = a[(Left + Right)/2];
        i = Left;j = Right;
        do
        {
            while( a[i]<x) i++;
            while(a[j]>x) j--;
            if(i<=j)
            {
                Swap(a[i],a[j]);
                    i++; j--;
            }
        }while (i<=j);
        if(i<Right) QuickSort(a,i,Right);
        if(Left<j) QuickSort(a,Left,j);

    }
   //after sort the array with function QuickSort, i was suggested to use 1 more       QuickSort 
   // to move evennumber to the top of the array
    void QSort(int a[],int Left,int Right)
    {
        int i, j, x;
        x = a[(Left + Right)/2];
        i = Left;j = Right;

        {
            while(a[i]%2==0 && a[i]<x ) i++;
            while(a[j]%2==1 && a[j]>x) j--;
            if(i<=j)
            {
                Swap(a[i],a[j]);
                    i++; j--;
            }
        }while (i<=j);
        for (i = 0; i<r;i++)
        {

        }
        if(i<Right) QSort(a,i,Right);
        if(Left<j) QSort(a,Left,j);
    }


    int main()
    {
          //n is numbers of integer array
        int a[Max],n;
            cout<<"Insert numbers of array: ";
            cin>>n;
            Input(a,n);
            cout<<"Array:\n";
            Display(a,n);
            cout<<endl;

            cout<<"Array after arrange: \n";
            QuickSort(a,0,n-1);
            Display(a,n);
            cout<<endl;

            cout<<"move even number to the top:\n";
            QSort(a,0,n-1);
            Display(a,n);

        return 0;
    }

Answer 1

So, the numbers 1 to 10 should be sorted as {2,4,6,8,10,9,7,5,3,1}?

Without looking at your code, I can tell you that you don’t need two quicksort functions.

Just let even numbers compare less than odd numbers. Numbers of the same parity compare as specified.