目录

右单旋：

左单旋：

左右双旋：

双旋平衡因子更新问题：

AVLTree完整代码：Gitee

右单旋：

void RotateR(Node* parent)//右旋
	{
		Node* subL = parent->_left;
		Node* subLR = subL->_right;

		parent->_left = subLR;
		if (subLR)
			subLR->_parent = parent;

		Node*ppNode = parent->_parent;

		subL->_right = parent;
		parent->_parent = subL;
        //这里要考虑subL的parent
		if (parent == _root)
		{
			_root = subL;
			subL->_parent = nullptr;
		}
		else
		{
			if (ppNode->_left == parent)
				ppNode->_left = subL;
			else
				ppNode->_right = subL;

            subL->_parent = ppNode;
		}
		parent->_bf = subL->_bf = 0;
	}

左单旋：

void RotateL(Node* parent)//左旋
	{
		Node* subR = parent->_right;
		Node* subRL = subR->_left;

		parent->_right = subRL;

		if (subRL)
		{
			subRL->_parent = parent;
		}
		Node* ppNode = parent->_parent;

		subR->_left = parent;
		parent->_parent = subR;

		if (parent == _root)
		{
			_root = subR;
			subR->_parent = nullptr;
		}
		else
		{
			if (ppNode->_left == parent)
				ppNode->_left = subR;
			else
				ppNode->_right = subR;

			subR->_parent = ppNode;
		}
		parent->_bf = subR->_bf = 0;
	}

左右双旋：

先左旋再右旋：先以30为旋转点，进行左单旋，再以90作为旋转点进行右单旋

先右旋再左旋：先以90为旋转点，进行右单旋，再以60作为旋转点进行左单旋

void RotateLR(Node* parent)
	{
		RotateL(parent->_left);
		RotateR(parent);
	}
	void RotateRL(Node* parent)
	{
		RotateRL(parent->_right);
		RotateL(parent);
	}

双旋平衡因子更新问题：

情况1：b插入，b的高度变成h

情况2：c插入，c的高度变成h

情况1和情况2如上图所画

情况3：

 60自己就是新增，bf = 0;

void RotateLR(Node* parent)
	{
		Node* subL = parent->_left;
		Node* subLR = subL->_right;

		int bf = subLR->_bf;

		if (bf == -1)
		{
			subL->_bf = 0;
			parent->_bf = 1;
			subLR->_bf = 0;
		}
		else if (bf == 1)
		{
			parent->_bf = 0;
			subL->_bf = -1;
			subLR -> _bf = 0;
		}
		else if (bf == 0)
		{
			parent->_bf = 0;
			subL->_bf = 0;
			subLR->_bf = 0;
		}
		else
		{
			assert(false);
		}
		RotateL(parent->_left);
		RotateR(parent);
	}
	void RotateRL(Node* parent)
	{
		Node* subR = parent->_right;
		Node* subRL = subR->_left;

		int bf = subRL->_bf;

		RotateR(parent->_right);
		RotateL(parent);

		if (bf == 1)
		{
			parent->_bf = -1;
			subR->_bf = 0;
			subRL->_bf = 0;
		}
		else if (bf == -1)
		{
			parent->_bf = 0;
			subR->_bf = 1;
			subRL->_bf = 0;
		}
		else if (bf == 0)
		{
			parent->_bf = 0;
			subR->_bf = 0;
			subRL->_bf = 0;
		}
		else
		{
			assert(false);
		}
	}

AVLTree完整代码：Gitee