How to construct a std::string from a std::vector?

Question

I\'d like to build a std::string from a std::vector.

I could use std::stringsteam, but imagine there is a s

Answer 1

Google Abseil has function absl::StrJoin that does what you need.

Example from their header file. Notice that separator can be also ""

//   std::vector<std::string> v = {"foo", "bar", "baz"};
//   std::string s = absl::StrJoin(v, "-");
//   EXPECT_EQ("foo-bar-baz", s);

Answer 2

You could use the std::accumulate() standard function from the <numeric> header (it works because an overload of operator + is defined for strings which returns the concatenation of its two arguments):

#include <vector>
#include <string>
#include <numeric>
#include <iostream>

int main()
{
    std::vector<std::string> v{"Hello, ", " Cruel ", "World!"};
    std::string s;
    s = accumulate(begin(v), end(v), s);
    std::cout << s; // Will print "Hello, Cruel World!"
}

Alternatively, you could use a more efficient, small for cycle:

#include <vector>
#include <string>
#include <iostream>

int main()
{
    std::vector<std::string> v{"Hello, ", "Cruel ", "World!"};
    std::string result;
    for (auto const& s : v) { result += s; }
    std::cout << result; // Will print "Hello, Cruel World!"
}