set_union(3C++) - set_union(3C++)
Standard C++ Library Copyright 1998, Rogue Wave Software, Inc.
NAMEset_union
- A basic set operation for constructing a sorted union.
SYNOPSIS
#include <algorithm>
template <class InputIterator1, class InputIterator2,
class OutputIterator>
OutputIterator
set_union (InputIterator1 first1, InputIterator1 last1,
InputIterator2 first2, InputIterator2 last2,
OutputIterator result);
template <;class InputIterator1, class InputIterator2,
class OutputIterator, class Compare>
OutputIterator
set_union (InputIterator1 first1, InputIterator1 last1,
InputIterator2 first2, InputIterator2 last2,
OutputIterator result, Compare comp);
DESCRIPTION
The_set_union algorithm constructs a sorted union of the elements from
the two ranges. It returns the end of the constructed range. set_union
is stable, which means that if an element is present in both ranges,
the one from the first range is copied. The result of set_union is
undefined if the result range overlaps with either of the original
ranges. Note that set_union does not merge the two sorted sequences. If
an element is present in both sequences, only the element from the
first sequence is copied to result. (Use the merge algorithm to create
an ordered merge of two sorted sequences that contains all the elements
from both sequences.)
set_union assumes that the sequences are sorted using the default com‐
parison operator less than (<), unless an alternative comparison opera‐
tor (comp) is provided.
COMPLEXITY
At most ((last1 - first1) + (last2 - first2)) * 2 -1 comparisons are
performed.
EXAMPLE
//
// set_unin.cpp
//
#include <algorithm>
#include <set>
#include <iostream>
using namespace std;
int main()
{
//Initialize some sets
int a2[6] = {2,4,6,8,10,12};
int a3[4] = {3,5,7,8};
set<;int, less<int> > even(a2+0, a2+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_unioncout <;< "The result of:" << endl << "{";
copy(small.begin(),small.end(),
ostream_iterator<int,char>(cout," "));
cout <;< "} union {";
copy(even.begin(),even.end(),
ostream_iterator<int,char>(cout," "));
cout <;< "} =" << endl << "{";
set_union(small.begin(), small.end(),
even.begin(), even.end(), res_ins);
copy(result.begin(),result.end(),
ostream_iterator<int,char>(cout," "));
cout <;< "}" << endl << endl;
return 0;
}
Program OutputThe result of:
{3 5 7 8 } union {2 4 6 8 10 12 } =
{2 3 4 5 6 7 8 10 12 }
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_intersection, set_difference, set_symmetric_differ‐
ence
Rogue Wave Software 02 Apr 1998 set_union(3C++)
