快速排序的擴展- 每n個作爲一組, n組按照一個屬性排序

	void QuickGroupSort(long long arr[], int low, int high, int nstep = 3) 
	{
		if (high <= low) return;
		int i = low;
		int j = high + 1;
		int key = arr[low*3+2];
		while (true)
		{
			/*從左向右找比key大的值*/
			while (arr[((++i)*nstep + nstep-1)] < key)
			{
				if (i == high) {
					break;
				}
			}
			/*從右向左找比key小的值*/
			while (arr[((--j)*nstep+nstep-1)] > key)
			{
				if (j == low) {
					break;
				}
			}
			if (i >= j) break;
			ExchangeValue(arr, i, j);
		}

		ExchangeValue(arr, low, j);
		QuickGroupSort(arr, low, j - 1);
		QuickGroupSort(arr, j + 1, high);
	}

	void ExchangeValue(long long arr[],int i,int j, int nstep = 3)
	{
		long long * tmp = new long long(nstep);
		memcpy(tmp, &arr[i*nstep], sizeof(long long)*nstep);
		memcpy(&arr[i*nstep], &arr[j*nstep], sizeof(long long)*nstep);
		memcpy (&arr[j*nstep], tmp,sizeof(long long)*nstep);
	}