What is the complexity of set_intersection in C++?
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28-04-2021 - |
Question
What is the complexity of the following code?
set<int> S1, S2, ans;
set_intersection(S1.begin(), S1.end(), S2.begin(), S2.end(), inserter(ans, ans.begin()))
where S1
and S2
are some non_empty sets and ans
is an empty set.
I know that inserting a sorted range into a set is linear; but is inserting using inserter linear too?
Solution
The inserter remembers where it last inserted each item and tries to insert the next item at the same place. This is O(1) if it's the right place.
Which means copying a sorted range to the inserter is linear overall, so you're good here.
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