Algorithm
A basic set operation for constructing a sorted intersection.
None
#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);
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.
At most ((last1 - first1) + (last2 - first2)) * 2 -1 comparisons are performed.
//
// 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 }
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.
includes, set, set_union, set_difference, set_symmetric_difference