Find the different characters present in a string

Question

Is there any way to find the all the unique characters present in a string without finding all the occurrences of the string ? For example, Let it be s

Answer 1

You can do that using std::sort, std::unique, std::string::erase

Note : original string will be modified [If you don't want that make a copy of it]

std::string str = "mississippi";
std::sort(std::begin(str), std::end(str));
auto last = std::unique(std::begin(str), std::end(str));
str.erase(last, std::end(str));

Answer 2

Make a set of characters and put all items from string to it, then you will have set with "alphabet" of your string.

E.g.:

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

int main(void)
{
    std::string a = "mississippi";
    std::set<char> alphabet;
    alphabet.insert(a.begin(), a.end());
    std::cout << "Set of chars has " << alphabet.size() << " items." << std::endl;
    for (auto a : alphabet)
    {
        std::cout << a << std::endl;
    }
}

Original string is not modified in that example and there is no need to pre-sort.

Answer 3

Sounds uncommon enough that it's not part of the STL.
I'd simply try iterating through the string and creating / incrementing the count of numbers in a Hashset. Then, grab all the Keys to determine unique values. Good Luck