C++Advanced-Maps and Sets-Short Words

#include<iostream>
#include<vector>
#include<string>
#include<sstream>
#include<algorithm>
#include<cctype>
#include<set>

std::vector<std::string> readInput() {
    std::vector< std::string > words;
    std::string line;
    getline(std::cin, line);
    std::istringstream istr(line);
    std::string currWord;
    while (istr >> currWord)
    {
        words.push_back(currWord);
    }

    return words;
}

char toLower(char inputChar) {
    return tolower(inputChar);
}

void transformToLowercase(std::vector< std::string >& words) {
    for (auto& word : words)
    {
        std::transform(word.begin(), word.end(), word.begin(), toLower);
    }
}

std::set<std::string> produceAnswerWords(const std::vector< std::string >& words) {
    std::set<std::string> answerWords;

    for (auto& word : words)
    {
        if (word.size() < 5)
        {
            answerWords.insert(word);
        }
    }

    return answerWords;
}

void printSolution(const std::set<std::string>& answerWords) {
    std::ostringstream ostr;
    for (const auto& word : answerWords)
    {
        ostr << word << ", ";
    }
    std::string answerStr = ostr.str();
    if (!answerWords.empty())
    {
        answerStr.pop_back();
        answerStr.pop_back();
    }
    std::cout << answerStr << std::endl;
}

int main() {
    auto wordsInput = readInput();
    transformToLowercase(wordsInput);
    const auto answerWords = produceAnswerWords(wordsInput);
    printSolution(answerWords);
    return 0;
}