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  1. #include <algorithm>
  2. #include <array>
  3. #include <iostream>
  4. #include <utility>
  5. #include <vector>
  6.  
  7. typedef std::pair<int, std::array<char, 3> > Element;
  8. std::vector< Element > v;
  9. std::vector< Element > result;
  10.  
  11. int main()
  12. {
  13.         v.push_back( Element(1, std::array<char, 3>{{'a', 'b', 'c'}}) );
  14.         v.push_back( Element(2, std::array<char, 3>{{'a', 'b', 'c'}}) );
  15.         v.push_back( Element(1, std::array<char, 3>{{'c', 'd', 'e'}}) );
  16.         v.push_back( Element(1, std::array<char, 3>{{'b', 'c', 'd'}}) );
  17.         v.push_back( Element(3, std::array<char, 3>{{'b', 'c', 'd'}}) );
  18.  
  19.         // O(N log(N) ) complexity
  20.         std::sort(v.begin(), v.end(), [](Element const& e1, Element const& e2){
  21.                 // compare the array part of the pair<int, array>
  22.                 return e1.second < e2.second; 
  23.         });
  24.  
  25.         // O(N) complexity
  26.         for (auto it = v.begin(); it != v.end();) {
  27.                 // find next element
  28.                 auto last = std::find_if(it, v.end(), [=](Element const& elem){
  29.                         return it->second != elem.second;     
  30.                 });
  31.  
  32.                 // accumulate the counts
  33.                 auto count = std::accumulate(it, last, 0, [](int sub, Element const& elem) {
  34.     		return sub + elem.first;
  35. 		});
  36.  
  37.                 // store count in result
  38.                 result.push_back( Element(count, it->second) );                  
  39.                 it = last;
  40.         }
  41.  
  42.         for (auto it = result.begin(); it != result.end(); ++it) {
  43.                 std::cout << it->first << " ";
  44.                 for (std::size_t i = 0; i < 3; ++i)
  45.                         std::cout << it->second[i] << " ";
  46.                 std::cout << "\n";
  47.         }
  48. }
Success #stdin #stdout 0s 3020KB
comments (?)
stdin
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Standard input is empty
stdout
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3 a b c 
4 b c d 
1 c d e
https://ideone.com/aDIS3A
language:
C++14 (gcc 8.3)
created:
11 years ago
visibility:
public

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