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  1. #include <iostream>
  2. #include <vector>
  3.  
  4. using namespace std;
  5.  
  6. //4. Implement count_if() yourself. Test it.
  7.  
  8. template<typename Iter, typename Predicate>
  9. typename iterator_traits<Iter>::value_type
  10. count_if(Iter first, Iter last, Predicate pred)
  11. {
  12.     typename iterator_traits<Iter>::value_type sum = 0;
  13.     for (Iter it = first; it != last; it++)
  14.     {
  15.         if (pred(*it)) // trouble here?
  16.         {
  17.             sum++;
  18.         }
  19.     }
  20.     return sum;
  21. }
  22.  
  23. int main()
  24. {
  25.     vector<int> v {1, 2, 3, 1, 5, -1};
  26.     cout << count_if(v.begin(), v.end(), [](int n) { return n > 1; }) << endl;
  27.     return 0;
  28. }
  29.  
Success #stdin #stdout 0s 15240KB
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https://ideone.com/GhFBpq
language:
C++ (gcc 8.3)
created:
8 years ago
visibility:
public

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