Question

I am trying to create a data structure called Disjoint Set. Looking at theory what i thought of is something like this :

std::vector<std::pair<int,std::set<int>>> DisjointSet;
for(auto i=0;i<10;++i) DisjointSet.push_back( std::make_pair(i,std::set<int>().insert(i)));

but this code gives which is beyond my understanding , so this is good design to make Disjoint Set. Also how do i get rid of these errors?

Answer 1

set::insert doesn’t return the set itself. You need to create the set beforehand, insert and then use it in make_pair. This does the trick with nearly no overhead for the copy using move:

std::vector< std::pair<int,std::set<int> > > DisjointSet;
for(auto i=0;i<10;++i) {
  std::set<int> tmp; tmp.insert(i);
  DisjointSet.push_back( std::make_pair(i,std::move(tmp)));
}