Library: Algorithms
Function
A basic set operation (algorithm) for constructing a sorted symmetric difference
#include <algorithm>
namespace std {
template <class InputIterator1, class InputIterator2,
class OutputIterator>
OutputIterator
set_symmetric_difference(InputIterator1 start1,
InputIterator1 finish1,
InputIterator2 start2,
InputIterator2 finish2,
OutputIterator result);
template <class InputIterator1, class InputIterator2,
class OutputIterator, class Compare>
OutputIterator
set_symmetric_difference(InputIterator1 start1,
InputIterator1 finish1,
InputIterator2 start2,
InputIterator2 finish2,
OutputIterator result,
Compare comp);
}
The algorithm set_symmetric_difference() constructs a sorted symmetric difference of the elements from the two ranges. This means that the constructed range includes copies of the elements that are present in the range [start1, finish1) (but not present in the range [start2, finish2)) and copies of the elements that are present in the range [start2, finish2) (but not in the range [start1, finish1)). It returns the end of the constructed range.
For example, suppose we have two sets:
1 2 3 4 5
and
3 4 5 6 7
The set_symmetric_difference() of these two sets is:
1 2 6 7
The result of set_symmetric_difference() is undefined if the result range overlaps with either of the original ranges.
set_symmetric_difference() assumes that the ranges are sorted using operator<(), unless an alternative comparison function object (comp) is provided.
Use the set_symmetric_difference() algorithm to obtain a result that includes elements that are present in the first set and not in the second.
At most ((finish1 - start1) + (finish2 - start2)) * 2 -1 comparisons are performed.
//
// set_s_di.cpp
//
#include <algorithm>
#include <set>
#include <iostream>
int main ()
{
#ifndef _RWSTD_NO_NAMESPACE
using namespace std;
#endif
// Initialize some sets.
int a1[] = {1,3,5,7,9,11};
int a3[] = {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_symmetric_difference.
cout << "The symmetric difference of:" << endl << "{";
copy(smalll.begin(),smalll.end(),
ostream_iterator<int,char,char_traits<char> >
(cout," "));
cout << "} with {";
copy(odd.begin(),odd.end(),
ostream_iterator<int,char,char_traits<char> >
(cout," "));
cout << "} =" << endl << "{";
set_symmetric_difference(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 symmetric difference of:
{3 5 7 8 } with {1 3 5 7 9 11 } =
{1 8 9 11 }
includes(), Iterators, set_union(), set_intersection(), set_difference()
ISO/IEC 14882:1998 -- International Standard for Information Systems -- Programming Language C++, Section 25.3.5.5