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template <class InputIterator,class T>typename iterator_traits<InputIterator>::difference_type    count (InputIterator first, InputIterator last,const T& val){typename iterator_traits<InputIterator>::difference_type ret = 0;while (first!=last) {if (*first == val) ++ret;    ++first;  }return ret;}

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// count algorithm example#include <iostream>// std::cout#include <algorithm>// std::count#include <vector>// std::vectorint main () {// counting elements in array:int myints[] = {10,20,30,30,20,10,10,20};// 8 elementsint mycount = std::count (myints, myints+8, 10);  std::cout <<"10 appears " << mycount <<" times.\n";// counting elements in container:  std::vector<int> myvector (myints, myints+8);  mycount = std::count (myvector.begin(), myvector.end(), 20);  std::cout <<"20 appears " << mycount  <<" times.\n";return 0;}

10 appears 3 times.20 appears 3 times.