【平衡树】【pb_ds】 bzoj1861 [Zjoi2006]Book 书架

需要用数组记录编号为i的书的位置，和位置i处的书的编号。

Code:

 #include<cstdio>
 #include<ext/pb_ds/assoc_container.hpp>
 #include<ext/pb_ds/tree_policy.hpp>
 using namespace std;
 using namespace __gnu_cxx;
 using namespace __gnu_pbds;
 tree<int,null_type,less<int>,rb_tree_tag,tree_order_statistics_node_update> T;
 typedef tree<int,null_type,less<int>,rb_tree_tag,tree_order_statistics_node_update>::iterator ITER;
 //往bzoj上交时，请将null_type改成null_mapped_type
 int Pos[],Val[],a,x,n,m;
 char op[];
 int main()
 {
     scanf("%d%d",&n,&m);
     for(int i=;i<=n;i++)
       {
         scanf("%d",&Val[i+]);
         Pos[Val[i+]]=i+;
         T.insert(i+);
       }
     for(int i=;i<=m;i++)
       {
         scanf("%s",op);
         if(op[]=='T')
           {
             scanf("%d",&a);
             int tmp=*T.find_by_order();
             T.erase(T.lower_bound(Pos[a]));
             Pos[a]=tmp-;
             Val[tmp-]=a;
             T.insert(tmp-);
           }
         else if(op[]=='B')
           {
             scanf("%d",&a);
             int tmp=*T.find_by_order(n-);
             T.erase(T.lower_bound(Pos[a]));
             Pos[a]=tmp+;
             Val[tmp+]=a;
             T.insert(tmp+);
           }
         else if(op[]=='I')
           {
             scanf("%d%d",&a,&x);
             if(x==)
               continue;
             ITER it=T.lower_bound(Pos[a]);
             ITER it_Beside=it;
             if(x==)
               it_Beside++;
             else
               it_Beside--;
             swap(Val[*it],Val[*it_Beside]);
             swap(Pos[Val[*it]],Pos[Val[*it_Beside]]);
           }
         else if(op[]=='A')
           {
             scanf("%d",&a);
             printf("%d\n",T.order_of_key(Pos[a]));
           }
         else
           {
             scanf("%d",&a);
             printf("%d\n",Val[*T.find_by_order(a-)]);
           }
       }
     return ;
 }