count [C++ Reference]
Keywords: stl,algorithm,count
Date: 2009-10-09T00:55:51-0700

## 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

Related Topics: accumulate, adjacent_difference, count_if, inner_product, partial_sum