Going from string to stringstream to vector<int>

Question

I've this sample program of a step that I want to implement on my application. I want to push_back the int elements on the string separately, into a vector. How can I?

#include <iostream>
#include <sstream>

#include <vector>

using namespace std;

int main(){

    string line = "1 2 3 4 5"; //includes spaces
    stringstream lineStream(line);


    vector<int> numbers; // how do I push_back the numbers (separately) here?
    // in this example I know the size of my string but in my application I won't


    }

Dormeuse

Answer 1

int num;
while (lineStream >> num) numbers.push_back(num);

Lester

Answer 2

This is a classic example of std::back_inserter.

copy(istream_iterator<int>(lineStream), istream_iterator<int>(),
     back_inserter(numbers));

You can create the vector right from the start on, if you wish

vector<int> numbers((istream_iterator<int>(lineStream)), 
                    istream_iterator<int>());

Remember to put parentheses around the first argument. The compiler thinks it's a function declaration otherwise. If you use the vector for just getting iterators for the numbers, you can use the istream iterators directly:

istream_iterator<int> begin(lineStream), end;
while(begin != end) cout << *begin++ << " ";

Improper

This is a perfect example, imho, of whats wrong with C++. In virtually every other language, this would be a split on ' ', followed by something like .toInt() for each element. Instead, we have an immensely complicated collection of templatized algorithms being applied. – Saum

I hear what you're saying dicroce. OTOH, this more complicated approach is faster, since you avoid creating a temporary array or list of strings, and also more powerful -- much the same code could be used to copy any sort of "range of values" (represented by a pair of iterators) into a vector. – Sludgy

C++11: vector<int> numbers(istream_iterator<int>(lineStream), {}); – Coffee

@KerrekSB yours is the first non-theoretic example I have seen for passing an initializer list to a deduced template parameter. Nice – Improper

Answer 3

string token;
char del = " ";
istringstream iss(line);   
while(getline(iss,token,del)) v1.push_back(stoi(token));

Yulandayule