C++ In a Nutshell

Name

set_union function template — Computes union of sorted ranges

Synopsis

template<typename InIter1, typename InIter2, typename OutIter>
  OutIter set_union(InIter1 first1, InIter1 last1, InIter2 first2, InIter2 last2,
                    OutIter result); 
template<typename InIter1, typename InIter2, typename OutIter, typename Compare>
  OutIter set_union(InIter1 first1, InIter1 last1, InIter2 first2, InIter2 last2,
                    OutIter result, Compare comp);

The set_union function template merges elements from the sorted ranges [first1, last1) and [first2, last2), copying the sorted, merged results to the range starting at result. If an element is present in both ranges, only one element is copied to the result range. If the input ranges contain duplicates, each occurrence of an element in an input range results in a copy in the result range. An iterator that points to one past the end of the result range is returned.

The result range must not overlap either source range.

The first version compares items using the < operator. The second version uses comp(X, Y) to test whether X < Y.

Figure 13-20 shows an example of a set union using multisets.

Figure 13-20. Computing the union of two sets

Technical Notes

Precondition: !(*(i + 1) < *i) for all i in [first1, last1 - 1) and !(*(j + 1) < *j) for all j in [first2, last2 - 1).

Postcondition: !(*(i + 1) < *i) for all i in [result, return - 1).

Complexity is linear: at most 2 × ((last1 ...