private static AvlTreeNode <T> RightRotate(AvlTreeNode <T> node)
{
var next = node.Left;
node.Left = next.Right;
next.Right = node;
return((AvlTreeNode <T>)next);
}
private static AvlTreeNode <T> LeftRotateTree(AvlTreeNode <T> node)
{
var right = (AvlTreeNode <T>)node.Right;
switch (right.Balance)
{
case Balance.RH:
node.Balance = right.Balance = Balance.EH;
return(LeftRotate(node));
case Balance.LH:
//左旋后右旋
node.Balance = right.Balance = Balance.EH;
node.Right = RightRotate((AvlTreeNode <T>)node.Right);
return(LeftRotate(node));
}
throw new ArgumentException("树结构错误");
}
public override bool Add(T item)
{
if (_root == null)
{
_root = new AvlTreeNode <T>(item)
{
Balance = Balance.EH
};
return(true);
}
bool top = false;
if (InsertNode((AvlTreeNode <T>)_root, null, item, ref top))
{
_count++;
return(true);
}
return(false);
}
private bool InsertNode(AvlTreeNode <T> node, AvlTreeNode <T> parent, T item, ref bool isHigh)
{
var flag = _comparer.Compare(item, node.Value);
if (flag == 0)
{
return(false);
}
bool isLeft = false;
if (flag > 0)
{
if (node.Right == null)
{
switch (node.Balance)
{
case Balance.EH:
node.Balance = Balance.RH;
break;
case Balance.LH:
node.Balance = Balance.EH;
break;
case Balance.RH:
node.Balance = Balance.RH;
break;
}
isHigh = node.Balance != Balance.EH;
node.Right = new AvlTreeNode <T>(item)
{
Balance = Balance.EH
};
return(true);
}
}
else
{
if (node.Left == null)
{
switch (node.Balance)
{
case Balance.EH:
node.Balance = Balance.LH;
break;
case Balance.LH:
node.Balance = Balance.LH;
break;
case Balance.RH:
node.Balance = Balance.EH;
break;
}
isHigh = node.Balance != Balance.EH;
node.Left = new AvlTreeNode <T>(item);
return(true);
}
isLeft = true;
}
var result = InsertNode((AvlTreeNode <T>)(isLeft ? node.Left : node.Right), node, item, ref isHigh);
if (result)
{
if (isHigh)
{
isHigh = false;
switch (node.Balance) //长高，需要平衡（需要判断长高的是左节点还是右节点）
{
case Balance.EH: //
node.Balance = isLeft ? Balance.LH : Balance.RH;
isHigh = true;
break;
case Balance.LH:
if (isLeft)
{
//右旋平衡
if (parent == null)
{
_root = RightRotateTree(node);
}
else
{
parent.Left = RightRotateTree(node);
}
}
else
{
node.Balance = Balance.EH;
}
break;
case Balance.RH:
if (isLeft)
{
node.Balance = Balance.EH;
}
else
{
//左旋平衡
if (parent == null)
{
_root = LeftRotateTree(node);
}
else
{
parent.Right = LeftRotateTree(node);
}
}
break;
}
}
}
return(result);
}