C++ string split and join

split_join.cpp

#include <string>

#define DOCTEST_CONFIG_IMPLEMENT_WITH_MAIN
#include "doctest.h"

std::vector<std::string> split(std::string const& str, std::string const& delim)
{
    std::vector<std::string> tokens;

    std::string::size_type s = 0;
    std::string::size_type e = str.find(delim, s);
    while (e != std::string::npos) {
        tokens.emplace_back(str.substr(s, e - s));
        s = e + delim.length();
        e = str.find(delim, s);
    }
    tokens.emplace_back(str.substr(s, e - s));

    return tokens;
}

std::string join(std::vector<std::string> const& strs, std::string const& delim)
{
    std::string ss;
    for (auto const& s : strs) {
        ss += ss.empty() ? s : delim + s;
    }
    return ss;
}


TEST_CASE("Split string with delimiter") {
    std::string s1 = "12, 23, 34";
    CHECK(split(s1, ", ") == std::vector<std::string>{"12", "23", "34"});
    CHECK(join(split(s1, ", "), ", ") == s1);
}