Count the number of elements in the range [ first , last ) that match value using operator== and add this count to n . Note that n is not automatically initialized to zero prior to the counting procedure.

Declaration


  
#include <algorithm>

template< class InputIterator, class T, class Size >
void count
  (
  InputIterator first,
  InputIterator last,
  const T& value,
  Size& n
  );

Complexity

Time complexity is linear, as ( last - first ) comparisons are performed. Space complexity is constant.

Example <ospace/osstd/examples/count0.cpp>


    #include <iostream>
#include <algorithm>

int numbers[ 10 ] = { 1, 2, 4, 1, 2, 4, 1, 2, 4, 1 };

void
main()
  {
  int result = 0;

  count( numbers, numbers + 10, 1, result );

  cout << "Found " << result << " 1's.\n";
  }

Found 4 1's.

Example <ospace/osstd/examples/count1.cpp>


    #include <iostream>
#include <algorithm>
#include <vector>

void
main()
  {
  vector< int > numbers( 100 );
  for ( int i = 0; i < 100; ++i )
    numbers[ i ] = i % 3;
  int elements = 0;

  count( numbers.begin(), numbers.end(), 2, elements );

  cout << "Found " << elements << " 2's.\n";
  }

Found 33 2's.

count

Library

Declaration

Complexity

Example <ospace/osstd/examples/count0.cpp>

Example <ospace/osstd/examples/count1.cpp>