平衡树封装模板

template<typename T> struct set{
	int rt,tot;
	std::vector<int>fix,sz,ls,rs,rub;
	std::vector<T>val;
	inline int new_node(T x){
		int p;
		if(rub.empty())p=++tot,fix.resize(p+1),sz.resize(p+1),ls.resize(p+1),rs.resize(p+1),val.resize(p+1);
		else p=*rub.rbegin(),rub.pop_back();
		fix[p]=rand(),val[p]=x,ls[p]=rs[p]=0,sz[p]=1;
		return p;
	}
	inline int size(){return tot-rub.size();}
	inline bool empty(){return tot==rub.size();}
	inline void clear(){
		rt=0,tot=0;
		fix.clear(),sz.clear(),ls.clear(),rs.clear(),rub.clear(),val.clear();
	}
	inline void upd(int x){
		sz[x]=1+sz[ls[x]]+sz[rs[x]];
	}
	int merge(int x,int y){
		if(!x || !y)return x|y;
		if(fix[x]<fix[y])return rs[x]=merge(rs[x],y),upd(x),x;
		else return ls[y]=merge(x,ls[y]),upd(y),y;
	}
	void split(int p,T a,int &x,int &y){
		if(!p){x=y=0;return;}
		if(val[p]<=a)x=p,split(rs[p],a,rs[p],y);
		else y=p,split(ls[p],a,x,ls[p]);
		upd(p);
	}
	inline T kth(int k){
		int x=rt;
		while(x){
			if(k<=sz[ls[x]])x=ls[x];
			else if(k==sz[ls[x]]+1)return val[x];
			else k-=sz[ls[x]]+1,x=rs[x];
		}
		return -1;
	}
	inline void insert(T val){
		int x,y;
		split(rt,val-1,x,y);
		rt=merge(merge(x,new_node(val)),y);
	}
	inline void erase(T val){
		int x,y,z;
		split(rt,val-1,x,y),split(y,val,y,z);
		if(y)rub.push_back(y);
		rt=merge(merge(x,merge(ls[y],rs[y])),z);
	}
	inline int rank(T val){
		int x,y;T ans;
		split(rt,val-1,x,y);
		ans=sz[x]+1,rt=merge(x,y);
		return ans;
	}
	inline T pre(T val){
		int x,y;T ans;
		split(rt,val-1,x,y);
		if(!x)return -1;
		rt=x,ans=kth(sz[x]),rt=merge(x,y);
		return ans;
	}
	inline T nxt(T val){
		int x,y;T ans;
		split(rt,val,x,y);
		if(!y)return -1;
		rt=y,ans=kth(1),rt=merge(x,y);
		return ans;
	}
};