stl:algorithm:count

count

Syntax:

    #include <algorithm>
    typename iterator_traits<input_iterator>::difference_type
    count( input_iterator start, input_iterator end, const TYPE& val );

The count() function returns the number of elements between start and end that match val.

For example, the following code uses count() to determine how many integers in a vector match a target value:

   vector<int> v;
   for( int i = 0; i < 10; i++ ) {
     v.push_back( i );
   }
 
   int target_value = 3;
   int num_items = count( v.begin(), v.end(), target_value );
 
   cout << "v contains " << num_items << " items matching " << target_value <<
  endl;

The above code displays the following output:

   v contains 1 items matching 3