How to convert a vector to string in C++

Question

Suppose I have a vector<int> and I want to convert it into string, what should I do? What I got from searching on the internet is

std::ostringstream oss;

if (!vec.empty())
{
  // Convert all but the last element to avoid a trailing ","
 std::copy(vec.begin(), vec.end()-1,
    std::ostream_iterator<int>(oss, ","));

// Now add the last element with no delimiter
oss << vec.back();
}

But I cannot understand what it means or how it works. Is there any other simple to understand way?

I don't get what this statement does `std::copy(vec.begin(), vec.end()-1, std::ostream_iterator(oss, ","));` — ronilp, May 20 '15 at 16:25
@ronilp there's no need for another way, this one works fine, `std::copy` is the most readable and idiomatic way to copy things. "I don't understand it" is not a reason to switch implementations. You'll need to **read the documentation.** — The Paramagnetic Croissant, May 20 '15 at 16:56
the way 0x499602D2 suggested is much more easier to understand. I was looking for such a way. — ronilp, May 20 '15 at 18:02

score 2 · Accepted Answer · answered May 20 '15 at 16:30

2

That code is only needed if you want to add a delimiter after every inserted integer, but even then it doesn't have to be that complicated. A simple loop and the use of to_string is far more readable:

std::string str;

for (int i = 0; i < vec.size(); ++i) {
    str += std::to_string(vec[i]);
    if (i+1 != vec.size()) { // if the next iteration isn't the last
        str += ", "; // add a comma (optional)
    }
}

answered May 20 '15 at 16:30

David G

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suppose no comma was required then, `str += ""` would be the change, right? – ronilp May 20 '15 at 16:31
@ronilp Then you wouldn't need the `if` statement at all, just the `str += to_string(vec[i])` part. – David G May 20 '15 at 16:32

Achilles Rasquinha · Answer 2 · 2015-05-20T16:54:17.383

0

Delimiting to numbers,

std::vector<int> v {0, 1, 2, 3, 4};
std::string s("");
for(auto i : v)
    s += std::to_string(i);

With a comma seperator

std::vector<int> v {0, 1, 2, 3, 4};
std::string s("");
for(auto i : v)
    s += std::to_string(i) + ",";
s.pop_back();

edited May 20 '15 at 16:54

answered May 20 '15 at 16:51

Achilles Rasquinha

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How to convert a vector to string in C++

2 Answers2