代码如下:

#include <iostream>
using namespace std;template <typename T>
struct AVLNode
{typedef AVLNode<T>  Node;AVLNode(const T &val = T()):_parent(nullptr),_left(nullptr),_right(nullptr),_val(nullptr),_bf(0){}Node *_parent;Node *_left;Node *_right;T _val;int _bf;
};template<typename T>
class AVLTreeNode
{
public:typedef AVLNode<T> Node;Node *LL_Rotate(Node *a){Node *b;b = a->_left;a->_left = b->_right;b->_right = a;a->_bf = b->_bf = 0;return b;}Node *RR_Rotate(Node *a){Node *b;b = a->_right;a->_right = b->_left;b->_left = a;a->_bf = b->_bf = 0;return b;}Node *LR_Rotate(Node *a){Node *b, *c;b = a->_left;c = b->_right;a->_left = c->_right;b->_right = c->_left;c->_left = b;c->_right = a;if (c->_bf == 1) {a->_bf = -1;b->_bf = 0;}else if (c->_bf == -1){a->_bf = 0;b->_bf = 1;}else{a->_bf = b->_bf = 0;}c->_bf = 0;return c;}Node *RL_Rotate(Node *a){Node *b, *c;b = a->_right;c = b->_left;a->_right = c->_left;b->_left = c->_right;c->_left = a;c->_right = b;if (c->_bf == 1){a->_bf = 0;b->_bf = -1;}else if (c->_bf == -1){a->_bf = 1;b->_bf = 0;}else{a->_bf = b->_bf = 0;}c->_bf = 0;return c;}void AVLInsert(Node *&pavlt, Node *s){Node *f, *a, *b, *p, *q;if (pavlt == nullptr)//没有根结点，那么插入的结点s就当作根结点{pavlt = s;return;}a = pavlt;//指针a记录离*s最近的平衡因子不为0的结点，f指向*a的父结点f = nullptr;p = pavlt;q = nullptr;while (p != nullptr){if (p->_val == s->_val) return;if (p->_bf != 0){a = p;f = q;}q = p;if (s->_val < p->_val) p = p->_left;else p = p->_right;}if (s->_val < q->_val) q->_left = s;else q->_right = s;p = a;while (p != s){if (s->_val < p->_val){p->_bf++;p = p->_left;}else{p->_bf--;p = p->_right;}}if (a->_bf > -2 && a->_bf < 2) return; //插入结点后，没有破坏树的平衡性if (a->_bf == 2){b = a->_left;if (b->_bf == 1) p = LL_Rotate(a);else p = LR_Rotate(a);}else{b = a->_right;if (b->_bf == 1) p = RL_Rotate(a);else p = RR_Rotate(a);}if (f == nullptr) pavlt = p;//原*a是AVL树的根else if (f->_left == a) f->_left = p;else f->_right = p;}void CreateTree(){int n;cin >> n;for (int i = 0; i < n; i++){Node *s = new Node;cin > s->_val;AVLInsert(_root, s);}}void InOrderTree(){InOrder(_root);cout << endl;}private:Node *_root;void InOrder(Node *cur){if (cur){InOrder(cur->_left);cout << cur->_val << " ";InOrder(cur->_right);}}
};