归并排序

template<typename T>
void __merge(T arr[], int left, int mid, int right)
{
	T *helper=new T[right - left + 1];
	for (int i = left; i <= right; i++)
	{
		helper[right-left] = arr[i];
	}
	int i = left, j = mid + 1;
	for (int k = left; k <= right; k++)
	{
		if (i > mid)
		{
			arr[k] = helper[j - left];
		}
		else if (j > right)
		{
			arr[k] = helper[i - left];
		}
		else if (helper[i - left] < helper[j - left])
		{
			arr[k] = helper[i - left];
			i++;
		}
		else
		{
			arr[k] = helper[j - left];
			i++;
		}
	}
}

template<typename T>
void __mergesort(T arr[], int left, int right)
{
	if (left >= right)
	{
		return;
	}
	int mid = (left + right) / 2;
	__mergesort(arr, left, mid);
	__mergesort(arr, mid + 1, right);
	__merge(arr, left, mid, right);
}

template<typename T>
void mergesort(T arr[], int len)
{
	__mergesort(arr, 0, len - 1);
}

生成了1000 0000个1-100之间的随机数，用希尔排序的话大概3s中搞定，归并排序花费的时间为12s，还是希尔排序比较吊=。=

转载于:https://my.oschina.net/0eb1/blog/863353