快速排序(Hoare 分割)

1. 使用 median of three得到分割点

２．当待排序数组的长度小于阈值（１０）的时候，切换到插入排序

代码：

void insertion_sort(int *a, int start, int end)
{
	int i, j;
	for(i = start + 1; i <= end; ++i)
	{
		int k = a[i];
		for( j = i - 1; (j >= start) && (a[j] > k); --j)
		{
			a[j+1] = a[j];
		}

		a[j+1] = k;
	}
}


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

int median(int *a, int start, int end)
{
	int mid = (start + end) / 2;
	if( a[mid] < a[start] )
	{
		swap(&a[mid], &a[start]);
	}

	if(a[end] < a[start])
	{

		swap(&a[start], &a[end]);
	}

	if(a[end] < a[mid])
	{
		swap(&a[end], &a[mid]);
	}

	swap(&a[mid], &a[end -1]);

	return a[end -1];
}

void _quick_sort(int *a, int start, int end)
{
	if( start + 10 <= end)
	{
		int i, j;
		for(;;)
		{
			i = start, j = end - 1;
			int med = median(a, start, end);
			while(a[++i] < med) {};
			while(a[--j] > med) {};

			if( i < j)
			{
				swap( &a[i], &a[j]);
			}
			else
			{
				break;		
			}
		}
		
		swap(&a[i], &a[end - 1]);
		printf("i = %d\n", i);
		_quick_sort(a, start, i - 1);
		_quick_sort(a, i + 1, end);
	}
	else
	{
		insertion_sort(a, start, end);
	}
}


void quick_sort(int *a, int size)
{
	_quick_sort(a, 0, size - 1);
}

标签：sort,分割,end,int,mid,start,swap,Hoare,排序
来源： https://blog.csdn.net/CaspianSea/article/details/89325244