p3369改代码20pts求助

#include <bits/stdc++.h>
using namespace std;
const int maxn=1e6+1e5+5,randmax=9999,randmin=1;
int cnt,root,lastans;
struct fhq_treap{
    int ls,rs;
    int data,val;
    int size;
}tr[maxn];
void inittreap(int data)
{
    cnt++;
    tr[cnt].size=1;
    tr[cnt].ls=0;tr[cnt].rs=0;
    tr[cnt].data=data;
    tr[cnt].val=rand()%randmax+randmin;
}
void upsize(int p)
{
    tr[p].size=tr[tr[p].ls].size+tr[tr[p].rs].size+1;
}
void split(int u,int x,int &l,int &r)
{
    if (!u)
    {
        l=0;r=0;return;
    }
    if (tr[u].data<=x)
    {
        l=u;
        split(tr[u].rs,x,tr[u].rs,r);
    }
    else
    {
        r=u;
        split(tr[u].ls,x,l,tr[u].ls);
    }
    upsize(u);
}
int merge(int l,int r)
{
    if (l==0||r==0) return l+r;
    if (tr[l].val>tr[r].val)
    {
        tr[l].rs=merge(tr[l].rs,r);
        upsize(l);
        return l;
    }
    else
    {
        tr[r].ls=merge(l,tr[r].ls);
        upsize(r);
        return r;
    }
}
void Insert(int x)
{
    int l,r;
    split(root,x,l,r);
    inittreap(x);
    int a=merge(l,cnt);
    root=merge(a,r);
}
void del(int x)
{
    int l,r,p;
    split(root,x,l,r);
    split(l,x-1,l,p);
    p=merge(tr[p].ls,tr[p].rs);
    root=merge(merge(l,p),r);
}
void paiming(int x)
{
    int l,r;
    split(root,x-1,l,r);
    lastans=tr[l].size+1;cout<<lastans<<endl;
    root=merge(l,r);
}
int kth(int u,int k)
{
    if (k==tr[tr[u].ls].size+1) return u;
    if (k<=tr[tr[u].ls].size) return kth(tr[u].ls,k);
    if (k>tr[tr[u].ls].size) return kth(tr[u].rs,k-tr[tr[u].ls].size-1);
}
void pre(int x)
{
    int l,r;
    split(root,x-1,l,r);
    lastans=tr[kth(l,tr[l].size)].data;
    cout<<lastans<<endl;
    root=merge(l,r);
 } 
void suf(int x)
{
    int l,r;
    split(root,x,l,r);
    lastans=tr[kth(r,1)].data;
    cout<<lastans<<endl;
    root=merge(l,r);
} 
int main()
{
    ios::sync_with_stdio(0);
    srand(time(0));
    int opt,x,n,m;cin>>n>>m;
    for (int i=1;i<=n;i++) {cin>>x;Insert(x);}
    for (int i=1;i<=m;i++)
    {
        cin>>opt>>x;
        x^=lastans;
        switch(opt)
        {
            case 1:Insert(x);break;
            case 2:del(x);break;
            case 3:paiming(x);break;
            case 4:lastans=tr[kth(root,x)].data;cout<<lastans<<endl;break;
            case 5:pre(x);break;
            case 6:suf(x);break;
        }
    }
    return 0;
}