Removing all spaces during tokenization

June 22, 2023

How can I remove all spaces between tokens in the following code?

#include <iostream>
#include <sstream>
using namespace std;
int main()
{
    string s[3] = {"a 1", "b    2", "c  3"};
    for (int i = 0; i < 3; i++) {
        stringstream ss(s[i]);
        string tok;
        while(getline(ss, tok, ' '))  // <-- need to fix
        {
            cout << tok << ".";  // <-- need to fix
        }
        cout << endl;
    }
    return 0;
}

The expected output is

a.1
b.2
c.3

But the code generates

a.1.
b....2.
c..3.

>Solution :

You could use formatted input from the stream instead of std::getline. Formatted input skips whitespaces by default:

#include <iostream>
#include <sstream>

int main() {
    std::string s[3] = {"a 1", "b    2", "c  3"};

    for (const auto& str : s) {
        std::istringstream ss(str);

        if (std::string tok; ss >> tok) {
            // at least one token read, print it
            std::cout << tok;

            // then read the rest and prepend them with '.' instead:
            while (ss >> tok) {
                std::cout << '.' << tok;
            }
        }
        std::cout << '\n';
    }
}

Output: