Count element in a sequence for a condition with algorithm count_if - C++ STL Algorithm

C++ examples for STL Algorithm:count_if

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Description

Count element in a sequence for a condition with algorithm count_if

Demo Code

#include <iostream> 
#include <algorithm> // algorithm definitions 
#include <numeric> // accumulate is defined here 
#include <vector> 
#include <iterator> 
using namespace std;

bool greater9(int); // predicate function prototype 

int main()/*from   w w w .  j  av  a2s  .  co  m*/
{
  const int SIZE = 10;
  int a1[SIZE] = { 1, 2, 3, 4, 5, 6, 7, 8, 9, 10 };
  vector< int > v(a1, a1 + SIZE); // copy of a1 
  ostream_iterator< int > output(cout, " ");

  // count number of elements in v2 that are greater than 9 
  int result = count_if(v.begin(), v.end(), greater9);
  cout << "\nNumber of elements greater than 9: " << result;

}

// determine whether argument is greater than 9 
bool greater9(int value)
{
  return value > 9;
} // end function greater9

Result


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