归并排序非递归写法

void _Merge(int arr[], int* tmp, int begin1, int end1, int begin2, int end2)
{
	int index = begin1;
	while (begin1 <= end1&&begin2 <= end2)
	{
		tmp[index++] = arr[begin1]<arr[begin2] ? arr[begin1++] : arr[begin2++];
	}
	while (begin1 <= end1)
	{
		tmp[index++] = arr[begin1++];
	}
	while (begin2 <= end2)
	{
		tmp[index++] = arr[begin2++];
	}
}


void MergeSort_NonR(int* A,int* tmp, int n)
{
	int step = 2;
	int left = 0, right = 0, mid = 0;
	
	while (step <= n)
	{
		int cur = 0;
		while (cur + step <= n)
		{
			right = cur + step-1, left = cur;
			 mid = (left + right) / 2;
			_Merge(A, tmp, left, mid, mid + 1, right);
			cur += step;
		}
		if (cur < n - 1)
		{
			 mid = (cur + n-1) / 2;
			_Merge(A, tmp, cur, mid, mid + 1, n);
		}
		step *= 2;
	}
	mid = (0 + n-1) / 2;
	_Merge(A, tmp, 0, mid, mid + 1, n - 1);
			
}

int* mergeSort(int* A, int n)
{
	if (A == NULL || n <= 0)
		return A;
	int* tmp = new int[n];
	memset(tmp, 0, sizeof(tmp));

	MergeSort_NonR(A, tmp, n);
	delete[] tmp;
	return A;

}