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  1. #include <iostream>
  2. #include <vector>
  3. #include<unordered_map>
  4. #include <string>
  5. using namespace std;
  6. #include<algorithm>
  7. #include<set>
  8.  
  9. #define Fast ios_base::sync_with_stdio(0); cin.tie(0); cout.tie(0);
  10. #define ll long long
  11.  
  12.  
  13. vector<pair<string,string>>ans;
  14.  
  15. unordered_map<string, string>mp;
  16. string find(string second) {
  17.     string name=second;
  18.     auto it = mp.find(second);
  19.     if ( it!= mp.end()) {
  20.         name=find( it->second);
  21.     }
  22.     return name;
  23. }
  24. void sol() {
  25.  
  26.     int n; cin >> n;
  27.     set<string>st;
  28.     while (n--) {
  29.         string old, newname; cin >> old >> newname; mp.insert({ old,newname });
  30.     }
  31.     for (auto it : mp) {
  32.         if (st.find(it.first) == st.end()) {
  33.             ans.push_back({ it.first, find(it.second) });
  34.             st.insert(it.second);
  35.         }
  36.     }
  37.     cout << ans.size() << endl;
  38.     reverse(ans.begin(), ans.end());
  39.     for (auto it : ans) {
  40.         cout << it.first << " " << it.second << endl;
  41.     }
  42. }
  43.  
  44. int main() {
  45.     Fast
  46.         int t = 1;
  47.     while (t--) {
  48.         sol();
  49.     }
  50.     return 0;
  51. }
Success #stdin #stdout 0.01s 5320KB
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https://ideone.com/Cy0u9a
language:
C++14 (gcc 8.3)
created:
16 days ago
visibility:
public

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