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  1. #include <iostream>
  2. #include <map>
  3.  
  4. int main()
  5. {
  6.     // The value_type of a map is pair<const Key, T>.
  7.     // To initialize a map an initializer list
  8.     // of pair<Key, T> objects must be specified.
  9.  
  10.     // To initialize a pair:
  11.     //
  12.     std::pair<int, int> p{9, 10};
  13.     std::cout << "pair:\n  (" << p.first << ", " << p.second << ")\n\n";
  14.  
  15.     // To initialize a simple map (no nesting)
  16.     // with value_type of pair<int, int>:
  17.     //
  18.     std::map<int, int> simple_map
  19.     {  // K  V
  20.         { 5, 6 },
  21.         { 7, 8 }
  22.     };
  23.     std::cout << "simple_map:\n";
  24.     for (auto const& i: simple_map)
  25.     {
  26.         std::cout << "  (" << i.first << ", " << i.second << ")\n";
  27.     }
  28.     std::cout << "\n";
  29.  
  30.     // To initialize a complex map (with nesting)
  31.     // with value_type of pair<const int, map<int, int>>
  32.     //
  33.     const std::map<int, std::map<int, int>> complex_map
  34.     {  // K       V
  35.        //       k  v
  36.         { 1, { {3, 4},
  37.                {5, 6} }
  38.         },
  39.         { 2, { {7, 8},
  40.                {8, 8},
  41.                {9, 0} }
  42.         }
  43.     };
  44.  
  45.     std::cout << "complex_map:\n";
  46.     for (auto const& mi: complex_map)
  47.     {
  48.         std::cout << "  (" << mi.first << ", ";
  49.         for (auto const& p: mi.second)
  50.         {
  51.             std::cout << '(' << p.first << ", " << p.second << ')';
  52.         }
  53.         std::cout << ")\n";
  54.     }
  55. }
  56.  
Success #stdin #stdout 0s 3036KB
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stdin
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Standard input is empty
stdout
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pair:
  (9, 10)

simple_map:
  (5, 6)
  (7, 8)

complex_map:
  (1, (3, 4)(5, 6))
  (2, (7, 8)(8, 8)(9, 0))
https://ideone.com/hCjtjP
language:
C++14 (gcc 8.3)
created:
11 years ago
visibility:
public

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