普通平衡树 - 替罪羊树

被学弟怼 : "你的博客上没有替罪羊树模板啊?"

#include <cstdio>
#include <vector>
#include <cstring>
#include <algorithm>
using namespace std;
typedef long long ll;
inline void read(int &x){
	x=0;char ch;bool flag = false;
	while(ch=getchar(),ch<'!');if(ch == '-') ch=getchar(),flag = true;
	while(x=10*x+ch-'0',ch=getchar(),ch>'!');if(flag) x=-x;
}
inline int cat_max(const int &a,const int &b){return a>b ? a:b;}
inline int cat_min(const int &a,const int &b){return a<b ? a:b;}
const int maxn = 100010;
const double alpha = 0.75;
struct Node{
	Node *ch[2];
	int key,siz,cnt;
	bool exist;
	void update(){
		siz = ch[0]->siz + ch[1]->siz + exist;
		cnt = ch[0]->cnt + ch[1]->cnt + 1;
	}
	bool pa(){
		return (ch[0]->cnt > cnt*alpha + 5) || (ch[1]->cnt > cnt*alpha + 5);
	}
};
struct STree{
	Node mem_poor[maxn];
	Node *tail,*root,*null;
	Node *bc[maxn];
	int bc_top;
	Node* NewNode(int key){
		Node *p = bc_top ? bc[--bc_top] : tail++;
		p->ch[0] = p->ch[1] = null;p->key = key;
		p->siz = p->cnt = 1;p->exist = true;
		return p;
	}
	void Travel(Node *p,vector<Node*>&v){
		if(p == null) return;
		Travel(p->ch[0],v);
		if(p->exist) v.push_back(p);
		else bc[bc_top++] = p;
		Travel(p->ch[1],v);
	}
	Node* Divide(vector<Node*>&v,int l,int r){
		if(l >= r) return null;
		int mid = l+r >> 1;
		Node *p = v[mid];
		p->ch[0] = Divide(v,l,mid);
		p->ch[1] = Divide(v,mid+1,r);
		p->update();return p;
	}
	void Rebuild(Node* &p){
		static vector<Node*>v;v.clear();
		Travel(p,v);p = Divide(v,0,v.size());
	}
	Node** Insert(Node* &p,int val){
		if(p == null){
			p = NewNode(val);
			return &null;
		}else{
			++(p->siz);++(p->cnt);
			Node **res = Insert(p->ch[val >= p->key],val);
			if(p->pa()) res = &p;
			return res;
		}
	}
	void Erase(Node *p,int id){
		--(p->siz);
		int x = p->ch[0]->siz + p->exist;
		if(p->exist && id == x){
			p->exist = false;
			return;
		}else{
			if(id <= x) Erase(p->ch[0],id);
			else Erase(p->ch[1],id - x);
		}return;
	}
	void init(){
		tail = mem_poor;
		null = tail++;
		null->ch[0] = null->ch[1] = null;
		null->cnt = null->siz = null->key = 0;
		root = null;bc_top = 0;
	}
	STree(){init();}
	void Insert(int val){
		Node** p = Insert(root,val);
		if(*p != null) Rebuild(*p);
	}
	int Rank(int val){
		Node *nw = root;
		int ret = 1;
		while(nw != null){
			if(nw->key >= val) nw = nw->ch[0];
			else{
				ret += nw->ch[0]->siz + nw->exist;
				nw = nw->ch[1];
			}
		}return ret;
	}
	int Kth(int k){
		Node *nw = root;
		while(nw != null){
			if(nw->ch[0]->siz + 1 == k && nw->exist) return nw->key;
			else if(nw->ch[0]->siz >= k) nw = nw->ch[0];
			else k -= nw->ch[0]->siz + nw->exist,nw = nw->ch[1];
		}
	}
	void Erase(int k){
		Erase(root,Rank(k));
		if(root->siz < alpha*root->cnt) Rebuild(root);
	}
	void Erase_kth(int k){
		Erase(root,k);
		if(root->siz < alpha*root->cnt) Rebuild(root);
	}
}Sky;
int main(){
	int n;read(n);
	int k,m;
	while(n--){
		read(k);read(m);
		switch (k){
			case 1: Sky.Insert(m);break;
			case 2: Sky.Erase(m);break;
			case 3:	printf("%d\n",Sky.Rank(m));break;
			case 4: printf("%d\n",Sky.Kth(m));break;
			case 5: printf("%d\n",Sky.Kth(Sky.Rank(m)-1));break;
			case 6: printf("%d\n",Sky.Kth(Sky.Rank(m+1)));break;
		}
	}
	getchar();getchar();
	return 0;
}