set_union()

Function

Constructs a sorted range beginning in the location pointed by result with the set union of the two sorted ranges [first1,last1) and [first2,last2).

The union of two sets is formed by the elements that are present in either one of the sets, or in both.

Elements from the second range that have an equivalent element in the first range are not copied to the resulting range.

The elements in the ranges shall already be sorted and the resulting range is also sorted accordingly.

Declaration

it = set_union (first1, last1, first2, last2, result);

first1, last1: Input iterators to the initial and final positions of the first sorted sequence. The range used is [first1,last1), which contains all the elements between first1 and last1, including the element pointed by first1 but not the element pointed by last1.

first2, last2: Input iterators to the initial and final positions of the second sorted sequence. The range used is [first2,last2), which contains all the elements between first2 and last2, including the element pointed by first2 but not the element pointed by last2.

result: Output iterator to the initial position of the range where the resulting sequence is stored.

Return value: Returns an iterator (it) to the end of the constructed range.

Example

#include <iostream>     
#include <algorithm>    // set_union, sort
#include <vector>       // vector
using namespace std;
int main () {
  int first[] = {5,10,15,20,25};
  int second[] = {50,40,30,20,10};
  vector<int> v(10);                      // 0  0  0  0  0  0  0  0  0  0
  vector<int>::iterator it;
  sort (first,first+5);     //  5 10 15 20 25
  sort (second,second+5);   // 10 20 30 40 50
  it=set_union (first, first+5, second, second+5, v.begin());  // 5 10 15 20 25 30 40 50  0  0
  v.resize(it-v.begin());                      // 5 10 15 20 25 30 40 50
  for (it=v.begin(); it!=v.end(); ++it) cout << ' ' << *it;
  cout <<endl;
  return 0;
}

Output:

 5 10 15 20 25 30 40 50