How can I get a std::set of characters in a string, as strings?

Question

I have a std::string. I want the set of unique characters in it, with each character represented as a std::string.

I can get the set of characters easily:

std::string some_string = ...
std::set<char> char_set(some_string.begin(), some_string.end());

And I could convert them to strings like this:

std::set<std::string> string_set;
for (char c: char_set) {
    string_set.emplace(1, c);
}

But such an approach seems awkward. Is there a better (preferrably standard-library one-liner) way to do this?

Answer 1

You can use:

std::for_each(some_string.begin(), some_string.end(),
              [&string_set] (char c) -> void { string_set.insert(std::string({c}));});

You can also use:

   for (char c: some_string)
   {
      string_set.insert(std::string{c});
   }

Working program:

#include <iostream>
#include <string>
#include <set>
#include <algorithm>

int main()
{
   std::string some_string = "I want the set of unique characters in it";
   std::set<std::string> string_set;
   for (char c: some_string)
   {
      string_set.insert(std::string{c});
   }

   for (std::string const& s: string_set)
   {
      std::cout << s << std::endl;
   }
}

Output:

I
a
c
e
f
h
i
n
o
q
r
s
t
u
w