[BZOJ3224] 替罪羊树版本

#include<cstdio>
#include<cstring>
#include<iostream>
using namespace std;
const double alpha=0.75;
int ls[200010],rs[200010],siz[200010],travel[200010],cnt[200010],stk[200010],v[200010];
int n,top,t1,root,goat;
bool exist[100010];
void dfs(int ro){
if (!ro) return;
dfs(ls[ro]);
if (exist[ro]) travel[++t1]=ro;
else stk[++top]=ro;
dfs(rs[ro]);
}
void build(int &ro,int l,int r){
int mid=(l+r)>>1;
ro=travel[mid];
if (l==r) {
siz[ro]=cnt[ro]=1;
ls[ro]=rs[ro]=0;
return ;
}
if (l<mid) build(ls[ro],l,mid-1);
else ls[ro]=0;
build(rs[ro],mid+1,r);
siz[ro]=siz[ls[ro]]+siz[rs[ro]]+1;
cnt[ro]=cnt[ls[ro]]+cnt[rs[ro]]+1;

}
void rebuild(int &ro){
t1=0;dfs(ro);
if (t1) build(ro,1,t1);
else ro=0;
}
void insert(int &ro,int x){
if (ro==0) {
ro=stk[top--];v[ro]=x;
siz[ro]=cnt[ro]=exist[ro]=1;
ls[ro]=rs[ro]=0;
return ;
}
siz[ro]++;cnt[ro]++;
if (x<=v[ro]) insert(ls[ro],x);
else insert(rs[ro],x);
if ((double)siz[ro]*alpha>(double)max(siz[ls[ro]],siz[rs[ro]])){
if (goat){
if (ls[ro]==goat) rebuild(ls[ro]);
else rebuild(rs[ro]);
goat=0;
}
}
else goat=ro;
}
void del_id(int &ro,int x){
if (exist[ro]&&x==siz[ls[ro]]+1){
exist[ro]=0;
siz[ro]--;
return ;
}
siz[ro]--;
if (x<=siz[ls[ro]]+exist[ro]) del_id(ls[ro],x);
else del_id(rs[ro],x-siz[ls[ro]]-exist[ro]);
}
int rank(int x){
int now=root;
int ans=1;
while (now){
if (v[now]>=x) now=ls[now];
else {
ans+=siz[ls[now]]+exist[now];
now=rs[now];
}
}
return ans;
}
void del_val(int x){
del_id(root,rank(x));
if ((double)siz[root]<(double)alpha*cnt[root]) rebuild(root);
}
int get_xth(int x){
int now=root;
while (now){
if (exist[now]&&x==siz[ls[now]]+1) return v[now];
else if (siz[ls[now]]>=x) now=ls[now];
else {
x-=siz[ls[now]]+exist[now];
now=rs[now];
}
}
}
int main(){
scanf("%d",&n);
root=0;
for (int i=400000;i>=1;i--) stk[++top]=i;
int opt,x;
for (int i=1;i<=n;i++){
scanf("%d%d",&opt,&x);
switch(opt){
case 1:insert(root,x);break;
case 2:del_val(x);break;
case 3:printf("%d\n",rank(x));break;
case 4:printf("%d\n",get_xth(x));break;
case 5:printf("%d\n",get_xth(rank(x)-1));break;
case 6:printf("%d\n",get_xth(rank(x+1)));break;
}
}
}