FHQtreap一直样例RE，求调玄关

#include<bits/stdc++.h>
using namespace std;
int n,rt,len=0;
struct node{int lc,rc,fa,val,key,siz;}t[100005];
void newnode(int v){
	len++;
	t[len].siz=1,t[len].val=v,t[len].key=rand();
	t[len].lc=t[len].rc=0;
	return;
}
void pushup(int x){
	t[x].siz=1+t[t[x].lc].siz+t[t[x].rc].siz;
	return;
}
void split(int rt,int x,int &rt1,int &rt2){
	if(!rt){
		rt1=rt2=0;
		return;
	}
	if(t[rt].val<=x) rt1=rt,split(t[rt].rc,x,t[rt].rc,rt2);
	else rt2=rt,split(t[rt].lc,x,rt1,t[rt].lc);
	pushup(rt);
	return;
}
int merge(int rt1,int rt2){
	if(!rt1) return rt2;
	if(!rt2) return rt1;
	if(t[rt1].key<t[rt2].key){
		t[rt1].rc=merge(t[rt1].rc,rt2);
		pushup(rt1);
		return rt1;
	}
	else{
		t[rt2].lc=merge(rt1,t[rt2].lc);
		pushup(rt2);
		return rt2;
	}
}
void insert(int v){
	int l,r;
	split(rt,v,l,r);
	newnode(v);
	rt=merge(merge(l,len),r);
	return;
}
void remove(int v){
	int x,y,z;
	split(rt,v,x,z);
	split(x,v-1,x,y);
	y=merge(t[y].lc,t[y].rc);
	rt=merge(merge(x,y),z);
	return;
}
int find_rk(int v){
	int l,r,ans;
	split(rt,v-1,l,r);
	ans=t[l].siz+1;
	rt=merge(l,r);
	return ans;
}
int find_kth(int rt,int k){
	if(k<=0||k>len) return 0;
	if(k<=t[t[rt].lc].siz) return t[find_kth(t[rt].lc,k)].val;
	else if(k==t[t[rt].lc].siz+1) return t[rt].val;
	else return t[find_kth(t[rt].rc,k-t[t[rt].lc].siz-1)].val;
}
int find_prev(int v){
	int l,r,ans;
	split(rt,v-1,l,r);
	ans=find_kth(l,t[l].siz);
	rt=merge(l,r);
	return t[ans].val;
}
int find_next(int v){
	int l,r,ans;
	split(rt,v,l,r);
	ans=find_kth(r,1);
	rt=merge(l,r);
	return t[ans].val;
}
signed main(){
	ios::sync_with_stdio(0);
	cin.tie(0),cout.tie(0);
	cin>>n;
	srand(time(0));
	while(n--){
		int op,x;
		cin>>op>>x;
		if(op==1){
			insert(x);
			//for(int i=1;i<=len;i++) cout<<t[i].lc<<' '<<t[i].rc<<endl;
		}
		if(op==2) remove(x);
		if(op==3) cout<<find_rk(x)<<'\n';
		if(op==4) cout<<find_kth(rt,x)<<'\n';
		if(op==5) cout<<find_prev(x)<<'\n';
		if(op==6) cout<<find_next(x)<<'\n';
	}
	return 0;
}