Standard C++ Library
Copyright 1998, Rogue Wave Software, Inc.

NAME

 
set_intersection
 
 - A basic set operation for constructing a sorted intersection.
 
 
 

SYNOPSIS

 
 
#include <algorithm>
template <class InputIterator1, class InputIterator2,

class OutputIterator>

OutputIterator

    set_intersection (InputIterator1 first1,

InputIterator1 last1,
InputIterator2 first2,
InputIterator last2,
OutputIterator result);

template <class InputIterator1, class InputIterator2,

class OutputIterator, class Compare>

OutputIterator

    set_intersection (InputIterator1 first1,

InputIterator1 last1,
InputIterator2 first2,
InputIterator2 last2,
OutputIterator result, Compare comp);
 
 
 

DESCRIPTION

 
 
The set_intersection algorithm constructs a sorted intersection of elements from the two ranges. It returns the end of the constructed range. When it finds an element present in both ranges, set_intersection always copies the element from the first range into result. This means that the result of set_intersection is guaranteed to be stable.   The result of set_intersection is undefined if the result range overlaps with either of the original ranges. 
 
set_intersection assumes that the ranges are sorted using the default comparison operator less than (<), unless an alternative comparison operator (comp) is provided. 
 
 
 

COMPLEXITY

 
 
At most ((last1 - first1) + (last2 - first2)) ∗ 2 -1 comparisons are performed. 
 
 
 

EXAMPLE

//
// set_intr.cpp
//
#include <algorithm>
#include <set>
#include <iostream>
using namespace std;
int main()

{

 
//Initialize some sets
int a1[10] = {1,3,5,7,9,11};
int a3[4]  = {3,5,7,8};
set<int, less<int> > odd(a1+0, a1+6),

result, small(a3+0,a3+4);

//Create an insert_iterator for result
insert_iterator<set<int, less<int> > >

res_ins(result, result.begin());

//Demonstrate set_intersection
cout << "The result of:" << endl << "{";
copy(small.begin(),small.end(),

ostream_iterator<int,char>(cout," "));

cout << "} intersection {";
copy(odd.begin(),odd.end(),

ostream_iterator<int,char>(cout," "));

cout << "} =" << endl << "{";
set_intersection(small.begin(), small.end(),

odd.begin(), odd.end(), res_ins);

copy(result.begin(),result.end(),

ostream_iterator<int,char>(cout," "));

cout << "}" << endl << endl;
return 0;

}
 

Program Output
 
 
 

 
The result of:
{3 5 7 8 } intersection {1 3 5 7 9 11 } =
{3 5 7 }
 
 
 

WARNINGS

 
 
If your compiler does not support default template parameters, then you always need to supply the Compare template argument and the Allocator template argument. For instance, you need to write:
 
set<int, less<int> allocator<int> >
 
instead of:
 
set<int>
 
If your compiler does not support namespaces, then you do not need the using declaration for std. 
 
 
 

SEE ALSO

 
 
includes, set, set_union, set_difference, set_symmetric_difference
 

Rogue Wave Software  —  Last change: 02 Apr 1998