Quicksort implementation in C.

quicksort.c

void quick_sort(int list[], int left, int right)
{
	if (left < right) {
		int pivot = (left + right) / 2; // left + (right - left) / 2 is safer to use for large lists
		pivot = partition(list, left, right, pivot);
		quick_sort(list, left, pivot - 1);
		quick_sort(list, pivot + 1, right);
	}
}

int partition(int list[], int left, int right, int pivot)
{
	int pivotVal = list[pivot];
	swap(&(list[pivot]), &(list[right]));
	
	int store = left;
	for (int i = left; i <= right - 1; i++) {
		if (list[i] < pivotVal) {
			swap(&(list[i]), &(list[store]));
			store++;
		}
	}
	swap(&(list[store]), &(list[right]));
	return store;
}

void swap(int *a, int *b)
{
	int c = *a;
	*a = *b;
	*b = c;
}