set_intersection()

Library:  Algorithms

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A basic set operation (algorithm) for constructing a sorted intersection

#include <algorithm>

namespace std {
  template <class InputIterator1, class InputIterator2, 
            class OutputIterator>
  OutputIterator  
  set_intersection(InputIterator1 start1, 
                   InputIterator1 finish1,
                   InputIterator2 start2, 
                   InputIterator2 finish2,
                   OutputIterator result);
  template <class InputIterator1, class InputIterator2, 
            class OutputIterator, class Compare>
  OutputIterator  
  set_intersection(InputIterator1 start1, 
                   InputIterator1 finish1,
                   InputIterator2 start2, 
                   InputIterator2 finish2, 
                   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 operator<(), unless an alternative comparison function object (comp) is provided.

At most ((finish1 - start1) + (finish2 - start2)) * 2 -1 comparisons are performed.

//
//  set_intr.cpp
//

#include <algorithm>
#include <set>
#include <iostream>

int main ()
{
#ifndef _RWSTD_NO_NAMESPACE
  using namespace std;
#endif


  // Initialize some sets.

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

  // Create an insert_iterator for result.

  insert_iterator<set<int, less<int>,allocator<int> > > 
                  res_ins(result, result.begin());

  // Demonstrate set_intersection.

  cout << "The result of:" << endl << "{";
  copy(smalll.begin(),smalll.end(), 
       ostream_iterator<int,char,char_traits<char> >
                       (cout," "));
  cout << "} intersection {";
  copy(odd.begin(),odd.end(),
       ostream_iterator<int,char,char_traits<char> >
                       (cout," "));
  cout << "} =" << endl << "{";

  set_intersection(smalll.begin(),smalll.end(),
                   odd.begin(),odd.end(),res_ins);
  copy(result.begin(),result.end(),
       ostream_iterator<int,char,char_traits<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 }

includes(), Iterators, set_union(), set_difference(), set_symmetric_difference()

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