Best way to get ints from a string with whitespace?

Question

I know this is simple, I just can\'t recall the best way to do this. I have an input like \" 5 15 \" that defines the x and y of a 2D vector array. I simply ne

Answer 1

I personally prefer the C way, which is to use sscanf():

const char* str = " 5 15 ";
int col, row;
sscanf(str, "%d %d", &col, &row); // (should return 2, as two ints were read)

Answer 2

Here's the stringstream way:

int row, col;
istringstream sstr(" 5 15 ");
if (sstr >> row >> col)
   // use your valid input

Answer 3

You can do it using a stringstream:

std::string s = " 5 15 ";
std::stringstream ss(s);

int row, column;
ss >> row >> column;

if (!ss)
{
    // Do error handling because the extraction failed
}

Answer 4

Assuming you've already validated that the input is really in that format, then

sscanf(str, "%d %d", &col, &row);

Answer 5

The C++ String Toolkit Library (StrTk) has the following solution to your problem:

int main()
{
   std::string input("5 15");
   int col = 0;
   int row = 0;
   if (strtk::parse(input," ",col,row))
      std::cout << col << "," << row << std::endl;
   else
      std::cout << "parse error." << std::endl;
   return 0; 
}

More examples can be found Here

Note: This method is roughly 2-4 times faster than the standard library routines and rougly 120+ times faster than STL based implementations (stringstream, Boost lexical_cast etc) for string to integer conversion - depending on compiler used of course.