count_if c++ example

c++ > algorithm > count_if

count_if returns the number of elements in a range whose values satisfy a specified condition.

template<class InputIterator, class Predicate>
   typename iterator_traits<InputIterator>::difference_typecount_if(
      InputIterator _First, 
      InputIterator _Last,
      Predicate _Pred
   );

Example

#include "stdafx.h"

#include <iostream>

#include <algorithm> 

#include <vector> 

using namespace std;

bool IsEven(int n)

{

       return ((n % 2) == 0);

}

int main() {

       std::vector<int> numbers;

       for (int i = 1; i<10; i++)

              numbers.push_back(i);

       int evencount = count_if(numbers.begin(), numbers.end(), IsEven);

       std::cout << "numbers contains " << evencount << " even values.\n";

       return 0;

}

Result: