Quick sort partition algorithm

Question

void partition(int *a, int size) {
   int pivot = a[0];
   int left = 0, right = 0;
   for(left = 1, right = size-1; left <= right; left++, right--) {
       if(a[lef         


        

Answer 1

You more or less answered your own question. You probably want to do something like this:

void partition(int *a, int size) {
    int pivot = a[0];
    int left, right;
    for(left = 1, right = size-1; left < right; )
    {
        if(a[left] > pivot && a[right] <= pivot)
        {
            swap(left, right, a);
        }
        if(a[left] <= pivot) left++;
        if(a[right] > pivot) right--;
    }
}

Answer 2

here is another option, little bit more similar to the original one

int partition(int arr[], int left, int right)
{
    int pivot = arr[left];
    while (left != right)
    {
        if (arr[left] > arr[right])
        {
            swap(arr[left], arr[right]);
        }
        if (pivot == arr[left])
            right--;
        else // Pivot == arr[right]
            left++;
    }
    return left;
}