Menu
Does the C++ STL set data structure have a set difference operator?
313
Sets are a type of associative container in which each element has to be unique because the value of the element identifies it. The values are stored in a specific sorted order i.e. either ascending or descending.
Set is an ordered sequence of unique keys whereas unordered_set is a set in which key can be stored in any order, so unordered. Set is implemented as a balanced tree structure that is why it is possible to maintain order between the elements (by specific tree traversal).
For a small number of elements, lookups in a set might be faster than lookups in an unordered_set . Even though many operations are faster in the average case for unordered_set , they are often guaranteed to have better worst case complexities for set (for example insert ).
Yes there is, it is in <algorithm> and is called: std::set_difference. The usage is:
#include <algorithm> #include <set> #include <iterator> // ... std::set<int> s1, s2; // Fill in s1 and s2 with values std::set<int> result; std::set_difference(s1.begin(), s1.end(), s2.begin(), s2.end(), std::inserter(result, result.end())); In the end, the set result will contain the s1-s2.
141
Yes, there is a set_difference function in the algorithms header.
Edits:
FYI, the set data structure is able to efficiently use that algorithm, as stated in its documentation. The algorithm also works not just on sets but on any pair of iterators over sorted collections.
As others have mentioned, this is an external algorithm, not a method. Presumably that's fine for your application.
33
If you love us? You can donate to us via Paypal or buy me a coffee so we can maintain and grow! Thank you!
Donate Us With
