排序算法：直接插入排序归并排序（递归与非递归实现）

Posted 2021-09-23 It‘s so simple

目录

• 1. 直接插入排序
• 2.归并排序
• • 2.1 递归
  • 2.2 非递归

---

1. 直接插入排序

void InsertSort(vector<int>& iv)
{
	for (int i = 0; i < iv.size() - 1; ++i)
	{
		int end = i;
		int tmp = iv[end + 1];
		while (end >= 0 && iv[end] > tmp)
		{
			iv[end + 1] = iv[end];
			--end;
		}
		iv[end + 1] = tmp;
	}
}

2.归并排序

2.1 递归

void _MergeSort(vector<int>& iv, int left, int right, vector<int>& tmp)
{
	if (left >= right)
		return;

	int mid = left + ((right - left) >> 1);

	_MergeSort(iv, left, mid, tmp);
	_MergeSort(iv, mid + 1, right, tmp);

	int begin1 = left;
	int end1 = mid;

	int begin2 = mid + 1;
	int end2 = right;

	int i = left;
	while (begin1 <= end1 && begin2 <= end2)
	{
		if (iv[begin1] < iv[begin2])
			tmp[i++] = iv[begin1++];
		else
			tmp[i++] = iv[begin2++];
	}

	while (begin1 <= end1)
	{
		tmp[i++] = iv[begin1++];
	}

	while (begin2 <= end2)
	{
		tmp[i++] = iv[begin2++];
	}

	int k = left;
	while (k <= right)
	{
		iv[k] = tmp[k];
		k++;
	}

}

void MergeSort(vector<int>& iv)
{
	vector<int> tmp(iv);
	_MergeSort(iv, 0, iv.size() - 1, tmp);
}

2.2 非递归

void _MergeSortNOR(vector<int>& iv, int left, int right)
{
	vector<int> tmp(iv.size());
	int n = iv.size();
	int gap = 1;
	while (gap < n)
	{
		for (int i = 0; i < n; i += gap*2)
		{
			int begin1 = i;
			int end1 = i + gap - 1;
			int begin2 = i + gap;
			int end2 = i + 2 * gap - 1;

			if (begin2 >= n)
				break;

			if (end2 >= n)
			{
				end2 = n - 1;
			}

			int j = begin1;
			while (begin1 <= end1 && begin2 <= end2)
			{
				if (iv[begin1] < iv[begin2])
				{
					tmp[j++] = iv[begin1++];
				}
				else
					tmp[j++] = iv[begin2++];
			}

			while (begin1 <= end1)
			{
				tmp[j++] = iv[begin1++];
			}

			while (begin2 <= end2)
			{
				tmp[j++] = iv[begin2++];
			}

			int k = i;
			while (k <= end2)
			{
				iv[k] = tmp[k];
				k++;
			}
		}
		gap *= 2;
	}
}