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
备注
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>