split_rk 函数会导致RE 求大佬查看原因

#include<bits/stdc++.h>
using namespace std;
struct NODE{
    int val,size,rank,cnt;
    NODE* son[2];
    NODE(int x):val(x){
        rank=rand();
        cnt=size=1;
        son[0]=son[1]=nullptr;
    }
    inline void upd_size(){
        size=cnt;
        if(son[0]!=nullptr)
            size+=son[0]->size;
        if(son[1]!=nullptr)
            size+=son[1]->size;
    }
};
pair<NODE*,NODE*> split_val(int val,NODE* cur){
    if(cur==nullptr)
        return {nullptr,nullptr};
    if(cur->val<val){
        auto temp=split_val(val,cur->son[1]);
        cur->son[1]=temp.first;
        cur->upd_size();
        return {cur,temp.second};
    }else{
        auto temp=split_val(val,cur->son[0]);
        cur->son[0]=temp.second;
        cur->upd_size();
        return {temp.first,cur};
    }
}
tuple<NODE*,NODE*,NODE*> split_rk(int rk,NODE* cur){
    if(cur==nullptr)return{nullptr,nullptr,nullptr};
    int ls_size=cur->son[0]==nullptr?0:cur->son[0]->size;
    if(rk<=ls_size){
        NODE *ls,*mid,*rs;
        tie(ls,mid,rs)=split_rk(rk,cur->son[0]);
        cur->son[0]=rs;
        cur->upd_size();
        return {ls,mid,cur};
    }else if(rk<=ls_size+cur->cnt){
        NODE *ls=cur->son[0],*rs=cur->son[1];
        cur->son[0]=cur->son[1]=nullptr;
        return {ls,cur,rs};
    }else{
        NODE *ls,*mid,*rs;
        tie(ls,mid,rs)=split_rk(rk-ls_size-cur->size,cur->son[1]);
        cur->son[1]=ls;
        cur->upd_size();
        return {cur,mid,rs};
    }
}
NODE* merge(NODE* a,NODE* b){
    if(a==nullptr)
        return b;
    if(b==nullptr)
        return a;
    if(a->rank<b->rank){
        a->son[1]=merge(a->son[1],b);
        a->upd_size();
        return a;
    }else{
        b->son[0]=merge(a,b->son[0]);
        b->upd_size();
        return b;
    }
}
NODE* insert(int x,NODE* cur){
    auto temp1=split_val(x,cur);
    auto temp2=split_val(x+1,temp1.second);
    if(temp2.first!=nullptr){
        temp2.first->cnt++;
        return merge(merge(temp1.first,temp2.first),temp2.second);
    }
    return merge(merge(temp1.first,new NODE(x)),temp2.second);
}
NODE* del(int x,NODE* cur){
    auto temp1=split_val(x,cur);
    auto temp2=split_val(x+1,temp1.second);
    if(temp2.first==nullptr)
        return merge(temp1.first,temp2.second);
    temp2.first->cnt--;
    if(!temp2.first->cnt)
        return  merge(temp1.first,temp2.second);
    return merge(merge(temp1.first,temp2.first),temp2.second);
}
int query_rk(int x,NODE* cur){
    auto temp1=split_val(x,cur);
    int res=temp1.first->size;
    cur=merge(temp1.first,temp1.second);
    return res;
}
int query_val(int rank,NODE* cur){
    NODE *ls,*mid,*rs;
    tie(ls,mid,rs)=split_rk(rank+1,cur);
    int res=mid->val;
    cur=merge(merge(ls,mid),rs);
    return res;
}
int pre_num(int x,NODE* cur){ 
    auto temp=split_val(x,cur);
    NODE *temp2=temp.first;
    while(temp2->son[1]!=nullptr)
        temp2=temp2->son[1];
    int res=temp2->val;
    cur=merge(temp.first,temp.second);
    return res;
}
int nex_num(int x,NODE* cur){
    auto temp=split_val(x+1,cur);
    NODE *temp1=temp.second;
    while(temp1->son[0]!=nullptr)
       temp1=temp1->son[0];
    int res=temp1->val;
    cur=merge(temp.first,temp.second);
    return res;
}
int n,opt,x;
int main(){
    NODE *ROOT=new NODE(INT_MIN);
    ROOT=merge(ROOT,new NODE(INT_MAX));
    cin>>n;
while(n--){
    scanf("%d%d",&opt,&x);
    switch(opt){
        case 1:
            ROOT=insert(x,ROOT);
            break;
        case 2:
            ROOT=del(x,ROOT);
            break;
        case 3:
            printf("%d\n",query_rk(x,ROOT));
            break;
        case 4:
            printf("%d\n",query_val(x,ROOT));
            break;
        case 5:
            printf("%d\n",pre_num(x,ROOT));
            break;
        case 6:
            printf("%d\n",nex_num(x,ROOT));
    }
}
}