[置顶] 排序算法的数组实现 -- 合并排序（三）

static const int Sentinel_Card = 100000;//哨兵，假设元素值都比它小
void static Merger(int *a, int p, int q, int r)
{
	int L_Size = q - p + 1;
	int R_Size = r - q;
	
	int *a1 = new int[L_Size + 1];
	int *a2 = new int[R_Size + 1];

	for (int i = 0; i < L_Size; i++)
		a1[i] = a[p + i];
	
	a1[L_Size] = Sentinel_Card; 
	
	for (int i = 0; i < R_Size; i++)
	{
		a2[i] = a[q + 1 + i];
	}
	a2[R_Size] = Sentinel_Card;
	
	int m = 0, n = 0;
	for (int i = p; i <= r; i ++)
	{
		if(a1[m] < a2[n])
		{
			a[i] = a1[m];
			m++;
		}
		else
		{
			a[i] = a2[n];
			n++;
		}

	}

}

void Merger_Sort(int *a, int p, int r)
{
	if(p < r)
	{
		int q = (p + r)/2;
		Merger_Sort(a, p, q);
		Merger_Sort(a, q + 1, r);
		Merger(a, p, q, r);
	}
}