# 11 Algorithms library [algorithms]

## 11.5 Sorting and related operations [alg.sorting]

### 11.5.5 Set operations on sorted structures [alg.set.operations]

#### 11.5.5.3set_intersection[set.intersection]

``` template <InputIterator I1, Sentinel<I1> S1, InputIterator I2, Sentinel<I2> S2, WeaklyIncrementable O, class Comp = less<>, class Proj1 = identity, class Proj2 = identity> requires Mergeable<I1, I2, O, Comp, Proj1, Proj2> O set_intersection(I1 first1, S1 last1, I2 first2, S2 last2, O result, Comp comp = Comp{}, Proj1 proj1 = Proj1{}, Proj2 proj2 = Proj2{}); template <InputRange Rng1, InputRange Rng2, WeaklyIncrementable O, class Comp = less<>, class Proj1 = identity, class Proj2 = identity> requires Mergeable<iterator_t<Rng1>, iterator_t<Rng2>, O, Comp, Proj1, Proj2> O set_intersection(Rng1&& rng1, Rng2&& rng2, O result, Comp comp = Comp{}, Proj1 proj1 = Proj1{}, Proj2 proj2 = Proj2{}); ```

Effects: Constructs a sorted intersection of the elements from the two ranges; that is, the set of elements that are present in both of the ranges.

Requires: The resulting range shall not overlap with either of the original ranges.

Returns: The end of the constructed range.

Complexity: At most 2 * ((last1 - first1) + (last2 - first2)) - 1 applications of the comparison function and projections.

Remarks: If [first1,last1) contains m elements that are equivalent to each other and [first2,last2) contains n elements that are equivalent to them, the first min(m, n) elements shall be copied from the first range to the output range, in order.