C++でのパズルの前後

理解を深めるために、次の実装を見てみましょう-

#include <bits/stdc++.h>
using namespace std;
void print_vector(vector<auto> v){
   cout << "[";
   for(int i = 0; i<v.size(); i++){
      cout << v[i] << ", ";
   }
   cout << "]"<<endl;
}
class Solution {
public:
   vector<string> beforeAndAfterPuzzles(vector<string>& phrases) {
      vector <string> ret;
      sort(phrases.begin(), phrases.end());
      unordered_map <string, vector <int> > m;
      int n = phrases.size();
      for(int i = 0; i < n; i++){
         string s = phrases[i];
         auto rspace = s.rfind(' ');
         m[rspace == string::npos ? s : s.substr(rspace + 1)].push_back(i);
      }
      for(int i = 0; i < n; i++){
         string s = phrases[i];
         auto lspace = s.find(' ');
         string x = (lspace == string::npos? s : s.substr(0, lspace));
         if(m.count(x)){
            vector <int>& v = m[x];
            for(int j = 0; j < v.size(); j++){
               if(v[j] != i){
                  ret.push_back(phrases[v[j]] + s.substr(x.size()));
               }
            }      
         }
      }
      sort(ret.begin(), ret.end());
      ret.erase(unique(ret.begin(), ret.end()), ret.end());
      return ret;
   }
};
main(){
   vector<string> v = {"mission statement","a quick bite to eat","a chip off the old block","chocolate bar","mission impossible","a man on a mission","block party","eat my words","bar of soap"};
   Solution ob;
   print_vector(ob.beforeAndAfterPuzzles(v));
}

入力

["mission statement","a quick bite to eat","a chip off the old block","chocolate bar","mission impossible","a man on a mission","block party","eat my words","bar of soap"]

出力

[a chip off the old block party, a man on a mission impossible, a man on a mission
statement, a quick bite to eat my words, chocolate bar of soap, ]