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  1. #include <utility>
  2. #include <vector>
  3. #include <algorithm>
  4. #include <string>
  5. #include <iostream>
  6.  
  7. template <typename container_type>
  8. typename container_type::iterator find_by_key(container_type& container, 
  9. 				const typename container_type::value_type::first_type& key) 
  10. {
  11.     typedef typename container_type::value_type element_type;
  12.  
  13.     return std::find_if(std::begin(container), std::end(container), 
  14.     			[&](const element_type& k) { return key == k.first; });
  15. }
  16.  
  17. int main()
  18. {
  19.     typedef std::pair<unsigned, std::string> element_type;
  20.  
  21.     std::vector<element_type> v =
  22.     {
  23.         {  1, "One"   },
  24.         {  3, "Three" },
  25.         {  5, "Five"  },
  26.         {  7, "Seven" },
  27.         {  9, "Nine"  },
  28.         { 10, "Ten"   },
  29.         {  8, "Eight" },
  30.         {  6, "Six"   },
  31.         {  4, "Four"  },
  32.         {  2, "Two"   }
  33.     };
  34.  
  35.     std::cout << "By key:\n";
  36.     for (unsigned i = 1; i < 11; ++i)
  37.     {
  38.         std::vector<element_type>::iterator it = find_by_key(v, i);
  39.  
  40.         std::cout << '\t' << i << " | ";
  41.  
  42.         if (it != v.end())
  43.             std::cout << it->second << '\n';
  44.         else
  45.             std::cout << "(null)\n";
  46.     }
  47.  
  48.     std::cout << "\n\nBy position:\n";
  49.     for (unsigned i = 0; i < v.size(); ++i)
  50.     {
  51.         std::cout << "\tpos: " << i << ": " ;
  52.         std::cout << v[i].first << " | " <<  v[i].second << '\n';
  53.     }
  54. }
Success #stdin #stdout 0s 3432KB
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stdin
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Standard input is empty
stdout
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By key:
	1 | One
	2 | Two
	3 | Three
	4 | Four
	5 | Five
	6 | Six
	7 | Seven
	8 | Eight
	9 | Nine
	10 | Ten


By position:
	pos: 0: 1 | One
	pos: 1: 3 | Three
	pos: 2: 5 | Five
	pos: 3: 7 | Seven
	pos: 4: 9 | Nine
	pos: 5: 10 | Ten
	pos: 6: 8 | Eight
	pos: 7: 6 | Six
	pos: 8: 4 | Four
	pos: 9: 2 | Two
https://ideone.com/37AlUC
language:
C++14 (gcc 8.3)
created:
10 years ago
visibility:
public

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