然而并不知道treap有什么用

#include
    
     #include
     
      #include
      
       #include
       
        using namespace std;struct node{    node* ch[2];    int r;    int v;    int s;    node(int v) :v(v)    {        r=rand();        ch[0]=ch[1]=NULL;        s=1;    }    bool operator < (const node &b)const     {        return r
        
          s;        if(ch[1]!=NULL)            s+=ch[1]-> s;    }    int cmp(int x) const    {        if(v==x)            return -1;        return x < v ? 0 : 1;    }};void rotato(node* &x,int base){    node *k=x->ch[base^1];    x->ch[base^1]=k->ch[base];    k->ch[base]=x;    x->sum();    k->sum();    x=k;    return ;}void insert(node* &x,int val){    if(x==NULL)        x=new node(val);    else    {        int d=(val
         
          v ? 0 : 1); insert(x->ch[d],val); if(x->ch[d]->r > x->r) rotato(x,d^1); } x->sum(); //printf("%d ",x->s);}void remove(node* &x,int val){ int d=x->cmp(val); if(d==-1) { node* u=x; if(x->ch[0]!=NULL&&x->ch[1]!=NULL) { int d1=(x->ch[0]->r > x->ch[1]-> r ? 1 : 0); rotato(x,d1); remove(x->ch[d1],val); } else if(x->ch[0]==NULL) x=x->ch[0]; else x=x->ch[1]; delete u; } else remove(x->ch[d],val); if(x!=NULL) x->sum();}int kth(node* x,int k){ //printf("%d",x->s); if(x==NULL|| k <=0|| k > x->s ) return 0; int s=(x->ch[0] == NULL ? 0 : x->ch[0]->s); if(k==s+1) return x->v; else if(k<=s) return kth(x->ch[0],k); else return kth(x->ch[1],k-s-1);}void merge(node* &src,node* &aim){ if(src->ch[0]!=NULL) merge(src->ch[0],aim); if(src->ch[1]!=NULL) merge(src->ch[1],aim); insert(aim,src->v); delete src; src=NULL;}void removetree(node* &x){ if(x->ch[0]!=NULL) removetree(x->ch[0]); if(x->ch[1]!=NULL) removetree(x->ch[1]); delete x; x=NULL;}int read(){ int s=0,f=1; char in=getchar(); while(in<'0'||in>'9') { if(in=='-') f=-1; in=getchar(); } while(in>='0'&&in<='9') { s=(s<<1)+(s<<3)+in-'0'; in=getchar(); } return s*f;}node *root;int add[200100],get[200100],num;int main(){ int m=read(),n=read(); num=1; root=NULL; for(int i=1;i<=m;i++) add[i]=read(); for(int i=1;i<=n;i++) get[i]=read(); for(int i=1;i<=m;i++) { insert(root,add[i]); //printf("%d",root->s); while(get[num]==i) { printf("%d\n",kth(root,num)); num+=1; } } return 0;}