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  1. #include <iostream>
  2. #include <iomanip>
  3. #include <map>
  4.  
  5. using namespace std;
  6.  
  7. class Array
  8. {
  9.  
  10.     struct proxy
  11.     {
  12.         int operator =(int v)
  13.         {
  14.             m[s] = v;
  15.             return v;
  16.         }
  17.  
  18.         operator int()
  19.         {
  20.             if (m.count(s)) return m[s];
  21.             return 0;
  22.         }
  23.  
  24.         proxy(Array*a, size_t s):m(a->m),s(s){}
  25.         map<size_t,int> &m;
  26.         size_t s;
  27.     };
  28. public:
  29.     Array() = default;
  30.  
  31.     proxy operator[](size_t s)
  32.     {
  33.         return proxy(this,s);
  34.     }
  35.  
  36.     size_t count() { return m.size(); }
  37.  
  38. private:
  39.     map<size_t,int> m;
  40. };
  41.  
  42. int main(int argc, const char * argv[])
  43. {
  44.     Array a;
  45.     a[5] = 4;
  46.     for(int i = 0; i < 7; ++i) cout << a[i] << " ";
  47.     cout << "\n" << a.count() << endl;
  48. }
  49.  
Success #stdin #stdout 0s 4532KB
comments (?)
stdin
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Standard input is empty
stdout
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0 0 0 0 0 4 0 
1
https://ideone.com/EmviR6
language:
C++14 (gcc 8.3)
created:
5 years ago
visibility:
public

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