What's better solution to separate user input by space in C++? - c++

Question

I'm reading C++ Primer and working on its exercise. It want me to get user's input and separate by space ' '. So I come up with 2 solution.
First solution:
vector<string> vector1;
string input;
string temp = ""; // temperary hold each word value in input.
string x1 = "";
char x2 = 'b';
x1 += x2;
cout << x1 << endl;
getline(cin, input);
input += " ";
for (string::size_type index = 0; index != input.size(); index++)
{
if (!isspace(input[index]))
{
temp += input[index];
}
else
{
if (temp.size() > 0)
{
vector1.push_back(temp);
temp = "";
}
}
}
Second solution
vector<string> vector1;
string input;
string temp = ""; // temperary hold each word value in input.
string x1 = "";
char x2 = 'b';
x1 += x2;
cout << x1 << endl;
getline(cin, input);
//input += " ";
for (string::size_type index = 0; index != input.size(); index++)
{
if (!isspace(input[index]))
{
temp += input[index];
}
else
{
if (temp.size() > 0)
{
vector1.push_back(temp);
temp = "";
}
}
}
if (!temp.empty())
{
vector1.push_back(temp);
}
The difference between them is first solution is add space to user input while second solution check that I don't add last word or not. I want to know which one is better solution for this problem?
If there're better solutions, please tell me.

Answer 1

I would write this:
std::vector<std::string> data;
std::copy(std::istream_iterator< std::string>(std::cin),
std::istream_iterator< std::string>(),
std::back_inserter(data));
It is almost same as #K-ballo's answer, except that I let std::copy read directly from input stream (i.e std::cin) rather than from std::stringstream.
Demo: http://www.ideone.com/f0Gtc
--
Or you could make use of vector's constructor, avoiding std::copy altogether:
std::vector<std::string> data(std::istream_iterator<std::string>(std::cin),
std::istream_iterator<std::string>());
And you're done! Demo : http://www.ideone.com/Szfes
If you find it difficult to read, then use this instead:
std::istream_iterator<std::string> begin(std::cin), end;
std::vector<std::string> data(begin, end);
Demo : http://www.ideone.com/PDcud

Answer 2

In C++, reading space-separated values is quite easy, and is built into the language. I may be wrong, but it looks like you are over-complicating things.
std::string line;
if (std::getline(std::cin, line)) {
std::stringstream ss(line);
std::vector<std::string> inputs_on_this_line(
std::istream_iterator<std::string>(ss)
, std::istream_iterator<std::string>() );
//do stuff with the strings on this line.
}

Answer 3

You can easily split the input from a stream into string separated values, and insert them into a vector with:
string input;
... get the input, perhaps with getline(cin, input); ...
stringstream input_stream( input );
vector<string> vector1;
std::copy(
(std::istream_iterator< std::string >( input_stream )), std::istream_iterator< std::string >()
, std::back_inserter( vector1 )
);
The std::istream_iterator< std::string > pair will iterate over the input_stream by extracting an std::string at a time (a string is read until a whitespace character is found). std::back_inserter will call push_back into your vector for each of those strings.