[luogu3835]可持久化平衡树

#include<stdio.h>
#include<stdlib.h>
#include<time.h>
int l[25000000],r[25000000],v[25000000],siz[25000000],fix[25000000],rt[500010],stk[500010],top,tot;
void update(int x){siz[x]=siz[l[x]]+siz[r[x]]+1;}
struct pair{
	int l,r;
	pair(int a=0,int b=0){l=a;r=b;}
};
int newnode(int d){
	int x;
	if(top){
		x=stk[top];
		top--;
	}else
		x=++tot;
	v[x]=d;
	l[x]=r[x]=0;
	siz[x]=1;
	fix[x]=rand()*rand();
	return x;
}
int copy(int u){
	int x;
	if(top){
		x=stk[top];
		top--;
	}else
		x=++tot;
	v[x]=v[u];
	l[x]=l[u];
	r[x]=r[u];
	siz[x]=siz[u];
	fix[x]=fix[u];
	return x;
}
pair split(int x,int k){
	if(x==0)return pair();
	if(k==0)return pair(0,copy(x));
	if(k==siz[x])return pair(copy(x),0);
	pair s;
	int n=copy(x);
	if(k<=siz[l[x]]){
		s=split(l[n],k);
		l[n]=s.r;
		s.r=n;
	}else{
		s=split(r[n],k-siz[l[x]]-1);
		r[n]=s.l;
		s.l=n;
	}
	update(n);
	return s;
}
int merge(int x,int y){
	if(x==0&&y==0)return 0;
	if(x==0)return copy(y);
	if(y==0)return copy(x);
	int n;
	if(fix[x]<fix[y]){
		n=copy(x);
		r[n]=merge(r[n],y);
	}else{
		n=copy(y);
		l[n]=merge(x,l[n]);
	}
	update(n);
	return n;
}
bool find(int x,int d){
	while(x){
		if(d==v[x])return 1;
		if(d<v[x])
			x=l[x];
		else
			x=r[x];
	}
	return 0;
}
int lt(int x,int d){
	int s=0;
	while(x){
		if(d<=v[x])
			x=l[x];
		else{
			s+=siz[l[x]]+1;
			x=r[x];
		}
	}
	return s;
}
int getkth(int x,int k){
	while(k!=siz[l[x]]+1){
		if(k<=siz[l[x]])
			x=l[x];
		else{
			k-=siz[l[x]]+1;
			x=r[x];
		}
	}
	return v[x];
}
#define inf 2147483647
int presc(int x,int d){
	int ans=-inf;
	while(x){
		if(v[x]<d){
			ans=v[x];
			x=r[x];
		}else
			x=l[x];
	}
	return ans;
}
int nexsc(int x,int d){
	int ans=inf;
	while(x){
		if(v[x]>d){
			ans=v[x];
			x=l[x];
		}else
			x=r[x];
	}
	return ans;
}
int main(){
	srand(time(0));
	int i,m,v,o,x;
	pair s,t;
	scanf("%d",&m);
	for(i=1;i<=m;i++){
		scanf("%d%d%d",&v,&o,&x);
		if(o==1){
			s=split(rt[v],lt(rt[v],x));
			rt[i]=merge(s.l,merge(newnode(x),s.r));
		}
		if(o==2){
			if(find(rt[v],x)){
				s=split(rt[v],lt(rt[v],x));
				t=split(s.r,1);
				rt[i]=merge(s.l,t.r);
				top++;
				stk[top]=t.l;
			}else
				rt[i]=rt[v];
		}
		if(o==3){
			printf("%d\n",lt(rt[v],x)+1);
			rt[i]=rt[v];
		}
		if(o==4){
			printf("%d\n",getkth(rt[v],x));
			rt[i]=rt[v];
		}
		if(o==5){
			printf("%d\n",presc(rt[v],x));
			rt[i]=rt[v];
		}
		if(o==6){
			printf("%d\n",nexsc(rt[v],x));
			rt[i]=rt[v];
		}
	}
}