題目描述：

 1 #include<iostream>
 2 #include<string>
 3 #include<set>
 4 #include<map>
 5 #include<stack>
 6 #include<vector>
 7 #include<algorithm>
 8 using namespace std;
 9 
10 #define ALL(x) x.begin(),x.end()
11 #define INS(x) inserter(x,x.begin())
12
 
 
13 typedef set<int> Set;
14 map<Set,int> IDcache; // 把集合映射成ID
15 vector<Set> Setcache; // 根據ID取集合
16 
17 int ID(Set x){
18     if(IDcache.count(x)) return IDcache[x] ;
19     Setcache.push_back(x) ;
20     return IDcache[x] = Setcache.size() - 1;
21 }
22 
23 int main(){
24
 
     int t ;
25     cin >> t ;
26     while(t--){
27         stack<int> s;
28         int n;
29         cin>> n;
30         for(int i=0;i<n;i++){
31             string op;
32             cin >> op;
33             if(op[0] == ‘P‘) s.push(ID(Set())) ;
34             else
 
 if (op[0] == ‘D‘) s.push(s.top());
35             else{
36                 Set x1 = Setcache[s.top()] ; s.pop();
37                 Set x2 = Setcache[s.top()] ;s.pop() ;
38                 Set x ;
39                 if (op[0] == ‘U‘) set_union (ALL(x1), ALL(x2), INS(x));
40                     if (op[0] == ‘I‘) set_intersection (ALL(x1), ALL(x2), INS(x));
41                 if (op[0] == ‘A‘) { x = x2; x.insert(ID(x1)); }
42                 s.push(ID(x));
43             }
44             cout << Setcache[s.top()].size() << endl;
45         }
46         cout << "***" << endl;
47     }
48     return 0;
49 }

集合棧計算機 （The SetStack Computer,ACM/ICPC NWERC 2006,UVa12096