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  1. #include <vector>
  2. #include <algorithm>
  3. #include <map>
  4. #include <string>
  5. #include <iostream>
  6. #include <iterator>
  7.  
  8. template <class T, class U>
  9. class sorting_map 
  10. { 
  11.     const std::map<T, U>& s_map;
  12.  public:
  13.     sorting_map(const std::map<T, U>& s_ ) : s_map(s_) {}
  14.     bool operator()(T x, T y) const { return s_map.at(x) < s_map.at(y); }
  15. };
  16.  
  17. using namespace std;
  18. int main()
  19. {
  20.     map<string, int> tmap = {{"a", 5}, {"b", 1}, {"c", 3}, {"e", 6}, {"f", 10}, {"g", 8}};
  21.  
  22.     vector<string> v = {"a", "b", "c", "f", "g"}; 
  23.  
  24.     cout << "Before sorting: ";
  25.     copy(v.begin(), v.end(), ostream_iterator<string>(cout, " "));
  26.     cout << '\n';
  27.  
  28.     sort(v.begin(), v.end(), sorting_map<string, int>(tmap));
  29.  
  30.     cout << "After sorting: ";
  31.     copy(v.begin(), v.end(), ostream_iterator<string>(cout, " "));
  32.     cout << '\n';
  33.  
  34.     map<string, int, sorting_map<string, int> > mymap3(tmap); 
  35.     mymap3["a"] = 100;
  36.     mymap3["b"] = 200;
  37.     mymap3["c"] = 300;
  38.     for(auto i = mymap3.begin(); i!=mymap3.end(); ++i)
  39.         std::cout << "mymap3[" << i->first << "] = " << i->second << '\n';
  40. }
  41.  
Success #stdin #stdout 0s 2992KB
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stdin
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Standard input is empty
stdout
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Before sorting: a b c f g 
After sorting: b c a g f 
mymap3[b] = 200
mymap3[c] = 300
mymap3[a] = 100
https://ideone.com/5uqqC
language:
C++14 (gcc 8.3)
created:
12 years ago
visibility:
public

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