題目具體描述見：https://uva.onlinejudge.org/index.php?option=com_onlinejudge&Itemid=8&page=show_problem&problem=3248php
算法流程以下：ios
C++11代碼以下：算法
1 #include<iostream> 2 #include<vector> 3 #include<string> 4 #include<map> 5 #include<set> 6 #include<stack> 7 #include<algorithm> 8 #include<iterator> 9 using namespace std; 10 11 typedef set<int> Set; 12 map<Set, int>IDcache; 13 vector<Set>Setcache; 14 15 // #define ALL(x) x.begin(),x.end() 16 // #define INS(x) inserter(x,x,begin()) 17 18 int ID(Set x) { 19 if (IDcache.count(x)) return IDcache[x]; //map中已有key(x),返回對應的value值 20 Setcache.push_back(x); //map中沒有key(x),將其插入vector 中 21 return IDcache[x] = Setcache.size() - 1; //將key(x)存入map中，並將對應的value賦值爲在vector中的下標 22 } 23 24 int main() { 25 int n, k; 26 stack<int>s; 27 cin >> n; 28 while (n--) { 29 cin >> k; 30 while (k--) { 31 string str; 32 cin >> str; 33 if (str[0] == 'P') s.push(ID(Set())); //空集入棧 34 else if (str[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 (str[0] == 'U') set_union(x1.begin(), x1.end(), x2.begin(), x2.end(), inserter(x, x.begin())); 40 if (str[0] == 'I') set_intersection(x1.begin(), x1.end(), x2.begin(), x2.end(), inserter(x, x.begin())); 41 if (str[0] == 'A') { x = x2; x.insert(ID(x1)); } //將x1的ID插入到x中 42 s.push(ID(x)); //合併後的x存入vector中，再將ID壓入棧中 43 } 44 cout << Setcache[s.top()].size() << endl; 45 } 46 cout << "***" << endl; 47 } 48 return 0; 49 }