Sorting of unordered_map

poorva2145 · January 12, 2020, 4:50am

Can we sort the unordered_map on the basis of VALUE in c++ using inbuilt sort function ?

Aayush · January 12, 2020, 6:32am

This is impossible from both a compilation and logical standpoint. From a type standpoint, std::sort requires:

-RandomIt must meet the requirements of ValueSwappable and RandomAccessIterator.
-The type of dereferenced RandomIt must meet the requirements of MoveAssignable and MoveConstructible.

From a logical standpoint, sorting an unordered container makes no sense.

If you want to “sort” your unordered_map, put them in a vector:

vector<pair<char, int> > elems(table.begin(), table.end());
sort(elems.begin(), elems.end());