iterating over an unordered_set

Question

I need help iterating over an unordered map in C++. I am trying to put the elements of the set into an array so that I can sort the array.

for(auto it=s.begin();it!=s.end();it++){
    a[i]=*it;
    i++;
}

Answer 1

Your are using many differen terms here.

• unordered_set
• unordered_map
• set
• array

So, it is a little bit unclear what you really want to do.

If you have a std::unordered_setand want to put the data into a std::set, then you can simply use its range constructor and write something like std::set<int> ordered(s.begin(),s.end());

The same would work with a std::vector which has also a range constructor. Arrays, either C-style or C++ std::array are more complicated, because you need to know the size of the original data in advance. Because: Arrays have a compile time definde fixed size.

For sorting std::maps or std::unordered_maps according to their "value" and not the key, you need to use a std::multiset with a special sorting functor or lambda. If you edit your question and give more details, then I will provide source code to you.