std::vector to string with custom delimiter

Use delimiter.c_str() as the delimiter:

copy(x.begin(),x.end(), ostream_iterator<int>(s,delimiter.c_str()));

That way, you get a const char* pointing to the string, which is what ostream_operator expects from your std::string.

C++11:

vector<string> x = {"1", "2", "3"};
string s = std::accumulate(std::begin(x), std::end(x), string(),
                                [](string &ss, string &s)
                                {
                                    return ss.empty() ? s : ss + "," + s;
                                });

Another way to do it:

#include <iostream>
#include <string>
#include <vector>
#include <sstream>
using namespace std;

template <typename T>
string join(const T& v, const string& delim) {
    ostringstream s;
    for (const auto& i : v) {
        if (&i != &v[0]) {
            s << delim;
        }
        s << i;
    }
    return s.str();
}

int main() {
    cout << join(vector<int>({1, 2, 3, 4, 5}), ",") << endl;
}

(c++11 range-based for loop and 'auto' though)