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:
1 #include<cstdio> 2 #include<ext/pb_ds/assoc_container.hpp> 3 #include<ext/pb_ds/tree_policy.hpp> 4 using namespace std; 5 using namespace __gnu_cxx; 6 using namespace __gnu_pbds; 7 tree<int,null_type,less<int>,rb_tree_tag,tree_order_statistics_node_update> T; 8 typedef tree<int,null_type,less<int>,rb_tree_tag,tree_order_statistics_node_update>::iterator ITER; 9 //往bzoj上交时，请将null_type改成null_mapped_type 10 int Pos[100001],Val[500001],a,x,n,m; 11 char op[7]; 12 int main() 13 { 14 scanf("%d%d",&n,&m); 15 for(int i=1;i<=n;i++) 16 { 17 scanf("%d",&Val[i+100000]); 18 Pos[Val[i+100000]]=i+100000; 19 T.insert(i+100000); 20 } 21 for(int i=1;i<=m;i++) 22 { 23 scanf("%s",op); 24 if(op[0]=='T') 25 { 26 scanf("%d",&a); 27 int tmp=*T.find_by_order(0); 28 T.erase(T.lower_bound(Pos[a])); 29 Pos[a]=tmp-1; 30 Val[tmp-1]=a; 31 T.insert(tmp-1); 32 } 33 else if(op[0]=='B') 34 { 35 scanf("%d",&a); 36 int tmp=*T.find_by_order(n-1); 37 T.erase(T.lower_bound(Pos[a])); 38 Pos[a]=tmp+1; 39 Val[tmp+1]=a; 40 T.insert(tmp+1); 41 } 42 else if(op[0]=='I') 43 { 44 scanf("%d%d",&a,&x); 45 if(x==0) 46 continue; 47 ITER it=T.lower_bound(Pos[a]); 48 ITER it_Beside=it; 49 if(x==1) 50 it_Beside++; 51 else 52 it_Beside--; 53 swap(Val[*it],Val[*it_Beside]); 54 swap(Pos[Val[*it]],Pos[Val[*it_Beside]]); 55 } 56 else if(op[0]=='A') 57 { 58 scanf("%d",&a); 59 printf("%d ",T.order_of_key(Pos[a])); 60 } 61 else 62 { 63 scanf("%d",&a); 64 printf("%d ",Val[*T.find_by_order(a-1)]); 65 } 66 } 67 return 0; 68 }