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  1. #include <iostream>
  2. #include <functional>
  3. #include <utility>
  4. #include <vector>
  5.  
  6. using namespace std;
  7.  
  8. template <typename T>
  9. auto vertex_triangle(const size_t index, const vector<pair<T, T>>& polygon) {
  10.     const auto& first = index == 0U ? polygon.back() : polygon[index - 1U];
  11.     const auto& second = polygon[index];
  12.     const auto& third = index == polygon.size() - 1U ? polygon.front() : polygon[index + 1U];
  13.  
  14.     return [&](auto& output){ output.push_back(first);
  15.                               output.push_back(second);
  16.                               output.push_back(third); };
  17. } 
  18.  
  19. int main() {
  20.     const vector<pair<int, int>> input { make_pair(1, 2), make_pair(2, 3), make_pair(3, 4), make_pair(4, 5) };
  21.     vector<pair<int, int>> output;
  22.  
  23.     for(size_t i = 0U; i < input.size(); ++i) {
  24.         vertex_triangle(i, input)(output);
  25.     }
  26.  
  27.     for(size_t i = 0U; i < output.size(); i += 3) {
  28.         cout << output[i].first << ',' << output[i].second << '\t' << output[i + 1U].first << ',' << output[i + 1U].second << '\t' << output[i + 2U].first << ',' << output[i + 2U].second << endl;
  29.     }
  30. }
Success #stdin #stdout 0s 16064KB
comments ()
stdin
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Standard input is empty
stdout
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4,5	1,2	2,3
1,2	2,3	3,4
2,3	3,4	4,5
3,4	4,5	1,2
https://ideone.com/bUmJmZ
language:
C++ (gcc 8.3)
created:
7 years ago
visibility:
public

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