//挖坑法 - 升序
int PartSort(int* a, int left, int right)
{
	int begin = left;
	int end = right;
	int key = a[begin];
	int pivot = begin;
 
	while (begin < end)
	{
		while (begin < end && a[end] >= key)
		{
			--end;
		}
		a[pivot] = a[end];
		pivot = end;
 
		while (begin < end && a[begin] <= key)
		{
			++begin;
		}
		a[pivot] = a[begin];
		pivot = begin;
	}
 
	pivot = begin;//當begin與end相遇，隨便把begin和end的值給pivot
	a[pivot] = key;
 
	return pivot;
}
 
void QuickSortNonR(int* a, int n)
{
	Stack st;
	StackInit(&st);//初始化棧
	StackPush(&st, n - 1);//入數組最后一個元素下標
	StackPush(&st, 0);//入數組第一個元素下標
 
	while (!StackEmpty(&st))//當棧不為空我們就進入循環
	{
		int left = StackTop(&st);//取出棧頂元素給left
		StackPop(&st);//出棧 - 刪除棧頂元素
 
		int right = StackTop(&st);
		StackPop(&st);
 
		int keyIndex =  PartSort(a, left, right);//使用挖坑法區間排序
 
		//[left, keyIndex - 1] keyIndex [keyIndex + 1, right]  -  分成子區間
 
		if (keyIndex + 1 < right)//因棧后進先出的特性，所以先入右區間
		{
			StackPush(&st, right);
			StackPush(&st, keyIndex + 1);
		}
 
		if (left < keyIndex - 1)
		{
			StackPush(&st, keyIndex - 1);
			StackPush(&st, left);
		}
	}
 
	StackDestory(&st);//銷毀棧
}

void MergeSortNonR(int* a, int n)
{
	int* tmp = (int*)malloc(sizeof(int) * n);
	if (tmp == NULL)
	{
		perror("malloc:");
		return;
	}
 
	int gap = 1;//gap為每組數據的個數，每次翻倍
 
	while (gap < n)
	{
		for (int i = 0; i < n; i += 2 * gap)
		{
			//可以看成 [i, i + gap - 1]  [i + gap, i + 2 * gap - 1]
			int begin1 = i, end1 = i + gap - 1;
			int begin2 = i + gap, end2 = i + 2 * gap - 1;
 
			//歸并過程中右半區間有可能不存在！
			if (begin2 >= n)
				break;
			//歸并過程中右半區間越界了，就修正下
			if (end2 >= n)
			{
				end2 = n - 1;
			}
			
			int index = i;
			while (begin1 <= end1 && begin2 <= end2)
			{
				if (a[begin1] < a[begin2])
				{
					tmp[index++] = a[begin1++];
				}
				else
				{
					tmp[index++] = a[begin2++];
				}
			}
 
			while (begin1 <= end1)
			{
				tmp[index++] = a[begin1++];
			}
			while (begin2 <= end2)
			{
				tmp[index++] = a[begin2++];
			}
 
			//拷貝進去
			for (int j = i; j <= end2; ++j)
			{
				a[j] = tmp[j];
			}
 		}
		gap *= 2;
	}
	free(tmp);
}