Algorithm
Basic set operation for sorted sequences.
#include <algorithm>
template <class InputIterator1, class InputIterator2, class OutputIterator> OutputIterator set_difference (InputIterator1 first1, InputIterator1 last1, InputIterator2 first2, InputIterator2 last2, OutputIterator result); template <class InputIterator1, class InputIterator2, class OutputIterator, class Compare> OutputIterator set_difference (InputIterator1 first1, InputIterator1 last1, InputIterator2 first2, InputIterator2 last2, OutputIterator result, Compare comp);
The set_difference algorithm constructs a sorted difference that includes copies of the elements that are present in the range [first1, last1) but are not present in the range [first2, last2). It returns the end of the constructed range.
As an example, assume we have the following two sets:
1 2 3 4 5
and
3 4 5 6 7
The result of applying set_difference is the set:
1 2
The result of set_difference is undefined if the result range overlaps with either of the original ranges.
set_difference assumes that the ranges are sorted using the default comparision operator less than (<), unless an alternative comparison operator (comp) is provided.
Use the set_symetric_difference algorithm to return a result that contains all elements that are not in common between the two sets.
At most ((last1 - first1) + (last2 - first2)) * 2 -1 comparisons are performed.
// // set_diff.cpp // #include <algorithm> #include <set> #include <iostream.h>
int main() {
//Initialize some sets int a1[10] = {1,2,3,4,5,6,7,8,9,10}; int a2[6] = {2,4,6,8,10,12};
set<int, less<int> > all(a1, a1+10), even(a2, a2+6), odd;
//Create an insert_iterator for odd insert_iterator<set<int, less<int> > > odd_ins(odd, odd.begin()); //Demonstrate set_difference cout << "The result of:" << endl << "{"; copy(all.begin(),all.end(), ostream_iterator<int>(cout," ")); cout << "} - {"; copy(even.begin(),even.end(), ostream_iterator<int>(cout," ")); cout << "} =" << endl << "{"; set_difference(all.begin(), all.end(), even.begin(), even.end(), odd_ins); copy(odd.begin(),odd.end(), ostream_iterator<int>(cout," ")); cout << "}" << endl << endl;
return 0; }
Output : The result of: {1 2 3 4 5 6 7 8 9 10 } - {2 4 6 8 10 12 } = {1 3 5 7 9 }
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>
instead of :
set<int>
includes, set, set_union, set_intersection, set_symmetric_difference