count (STL Samples)

Illustrates how to use the count Standard Template Library (STL) function in Visual C++.

template<class InputIterator, class T> inline
   size_t count(
      InputIterator First,
      InputIterator Last,
      const T& Value
   )

Remarks

注意

The class/parameter names in the prototype do not match the version in the header file. Some have been modified to improve readability.

The count algorithm counts the number of elements in the range [First, Last +1) that match Value and returns the number of matching elements.

Example

// count.cpp
// compile with: /EHsc
//
// Functions:
//
//    count  - Count items in a range that match a value.

// disable warning C4786: symbol greater than 255 character,
// okay to ignore
#pragma warning(disable: 4786)

#include <iostream>
#include <algorithm>
#include <functional>
#include <string>
#include <vector>

using namespace std;


int main()
{
    const int VECTOR_SIZE = 8 ;

    // Define a template class vector of strings
    typedef vector<string > StringVector ;

    //Define an iterator for template class vector of strings
    typedef StringVector::iterator StringVectorIt ;

    StringVector NamesVect(VECTOR_SIZE) ;   //vector containing names

    string value("Sea") ;  // stores the value used
                           // to count matching elements

    StringVectorIt start, end, it ;

    ptrdiff_t result = 0 ;   // stores count of elements
                       // that match value.

    // Initialize vector NamesVect
    NamesVect[0] = "She" ;
    NamesVect[1] = "Sells" ;
    NamesVect[2] = "Sea" ;
    NamesVect[3] = "Shells" ;
    NamesVect[4] = "by" ;
    NamesVect[5] = "the" ;
    NamesVect[6] = "Sea" ;
    NamesVect[7] = "Shore" ;

    start = NamesVect.begin() ;   // location of first
                                  // element of NamesVect

    end = NamesVect.end() ;       // one past the location
                                  // last element of NamesVect

    // print content of NamesVect
    cout << "NamesVect { " ;
    for(it = start; it != end; it++)
        cout << *it << " " ;
    cout << " }\n" << endl ;

    // Count the number of elements in the range [first, last +1)
    // that match value.
    result = count(start, end, value) ;

    // print the count of elements that match value
    cout << "Number of elements that match \"Sea\" = "
        << result << endl  ;
}

Output

NamesVect { She Sells Sea Shells by the Sea Shore  }

Number of elements that match "Sea" = 2

Requirements

Header: <algorithm>

See Also

Concepts

Standard Template Library Samples