set_intersection

Algorithm

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• Complexity
• Example
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Basic set operation for sorted sequences.

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.h>
 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, a1+6),
                        result, small(a3,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;
 }

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 need to always supply the Compare template argument and the Allocator template argument. For instance, you will need to write :

set<int, less<int> allocator<int> >

instead of :

set<int>

includes, set, set_union, set_difference, set_symmetric_difference

©Copyright 1996, Rogue Wave Software, Inc.