- 迭代器中序遍历整棵树，++或--为前驱后继
- 可重复插入，查找，排名（<或<=），删除，大小，相同元素个数
- 功能超全的 stl-like splay 平衡树，摈弃平板电视，还不快收入囊中！
- 插入删除的方式为new/delete，不喜勿喷~
#include <algorithm> using namespace std; template<typename T> class splay_tree_iterator; template<typename T, typename _Less = less<T>, typename _Equ = equal_to<T>> class splay_tree { public: friend class splay_tree_iterator<T>; typedef _Less lesscmp; typedef _Equ equcmp; typedef splay_tree_iterator<T> iterator; splay_tree() : _r(nullptr) { } iterator root() { return iterator(_r); } iterator begin() { _node *p = _r; if(!p) return iterator(nullptr); while(p->s[0]) p = p->s[0]; return iterator(p); } iterator end() { iterator k = _end(); return ++k; } void insert(T o) { _node *k = _insert(nullptr, _r, o); if(k != _r) _splay(k); } iterator find(T o) { _node *k = _find(_r, o); if(!k) return end(); return iterator(k); } void erase(T o) { _node *k = _find(_r, o); if(!k) return; _splay(k); if(k->cnt > 1) { --k->cnt, --k->size; return; } _node *p = k->_prec(); if(p) { _splay(p), p->s[1] = k->s[1]; if(p->s[1]) p->s[1]->f = p; delete k; } else if((p = k->_succ())) _splay(p), delete k; else delete k, _r = nullptr; k = nullptr; if(p) _sync(p); } size_t size() { return _r ? _r->size : 0; } size_t rank(T o, bool equ = false) { return _rank(_r, o, equ); } private: lesscmp _cl; equcmp _ce; struct _node { T v; int cnt, size; _node *f, *s[2]; _node * _succ() { _node *k = this; if(!k->s[1]) { for(; k->f && k->f->s[1] == k; k = k->f); return k->f; } else { for(k = k->s[1]; k->s[0]; k = k->s[0]); return k; } } _node * _prec() { _node *k = this; if(!k->s[0]) { for(; k->f && k->f->s[0] == k; k = k->f); return k->f; } else { for(k = k->s[0]; k->s[1]; k = k->s[1]); return k; } } } *_r; inline void _sync(_node *k) { k->size = (k->s[0] ? k->s[0]->size : 0) + (k->s[1] ? k->s[1]->size : 0) + k->cnt; } inline void _rotate(_node *k) { _node *l = k->f, *m = l->f; bool isr = l->s[1] == k; if(m) m->s[m->s[1] == l] = k; k->f = m; l->s[isr] = k->s[!isr], k->s[!isr] = l, l->f = k; if(l->s[isr]) l->s[isr]->f = l; _sync(l), _sync(k); } void _splay(_node *k) { while(k->f) { _node *l {k->f}, *m {l->f}; if(!m) _rotate(k); else if(m->s[1] == l ^ l->s[1] == k) _rotate(k), _rotate(k); else _rotate(l), _rotate(k); } _r = k; } _node * _insert(_node *f, _node *&k, T o) { if(!k) return k = new _node { o, 1, 1, f, nullptr, nullptr }; ++k->size; if(_cl(k->v, o)) return _insert(k, k->s[1], o); if(!_ce(k->v, o)) return _insert(k, k->s[0], o); ++k->cnt; return k; } _node *_find(_node *k, T o) { if(!k) return nullptr; if(_cl(k->v, o)) return _find(k->s[1], o); if(!_ce(k->v, o)) return _find(k->s[0], o); return k; } iterator _end() { _node *p = _r; if(!p) return nullptr; while(p->s[1]) p = p->s[1]; return iterator(p); } size_t _rank(_node *k, T o, bool equ) { if(!k) return 0; if(_cl(k->v, o)) return _rank(k->s[1], o, equ) + (k->s[0] ? k->s[0]->size : 0) + k->cnt; if(!_ce(k->v, o)) return _rank(k->s[0], o, equ); return (k->s[0] ? k->s[0]->size : 0) + (equ ? k->cnt : 1); } }; template<typename T> class splay_tree_iterator : iterator<bidirectional_iterator_tag, T> { public: friend class splay_tree<T>; splay_tree_iterator(const splay_tree_iterator<T> &i) : _n(i._n), _p(i._p) { } splay_tree_iterator &operator++() { _p = _n, _n = _n->_succ(); return *this; } splay_tree_iterator operator++(int) { splay_tree_iterator p(*this); _p = _n, _n = _n->_succ(); return p; } splay_tree_iterator &operator--() { if(!_n) _n = _p, _p = nullptr; else _n = _n->_prec(); return *this; } splay_tree_iterator operator--(int) { splay_tree_iterator p(*this); if(!_n) _n = _p, _p = nullptr; else _n = _n->_prec(); return p; } T &operator *() { return _n->v; } T *operator ->() { return &(_n->v); } size_t count() { return _n->cnt; } bool operator != (const splay_tree_iterator<T> &i) { return this->_n != i._n; } bool operator == (const splay_tree_iterator<T> &i) { return !(*this != i); } private: typedef typename splay_tree<T>::_node ptr; splay_tree_iterator(ptr *p) : _n(p), _p(nullptr) { } ptr *_n, *_p; };原文：https://www.cnblogs.com/js2xxx/p/9345922.html