Getting rid of white spaces (C++)

Question

My code allows the user to input numbers, it sorts them, and outputs them in order.

Example input: 25,1,3-6
Example output: 1,3,4,5,6,25

However when the user inputs something like 2 5,1,3-6, and if there is a space in a case like 3 - 6, the program doesn't work.

I used cin>>ws; to try to get rid of whitespace, however it is not working.

Here is the part of the code related to this issue (there are a few other functions I did not include, unless they seem to the source of the issue):

#include <iostream>     
#include <string>      
#include <cctype>     
#include <vector>

using namespace std;

void get_nums(vector<int>& num_vec);

int main () 
{
    int num1;
    int num2;
    cout << "\n Please, enter your HW: ";
    vector<int> num_vec;
    cin>>ws;
    cout.flush(); 
    do
    {
        cin>>ws;
        cin>>num1; 
        num_vec.push_back(num1);
        if(cin.peek() == ',')
        {       
            cin.ignore();
        }
        else if(cin.peek() == '-')
        {
            cin.ignore();
            cin>>num2;
            for(++num1; num1<=num2; num1++)
            {
                num_vec.push_back(num1);
            } 
            if(cin.peek() == ',')
            {
                cin.ignore();
            }       
        }
    }
    while (cin.peek() != '\n');

    cout<< "\n Do Problems: ";
    for(int z=0; z<num_vec.size(); z++)
    {
        if(z+1==num_vec.size())
        {
            cout<<num_vec[z];   
        }
        else if(z+2==num_vec.size())
        {
            cout<<num_vec[z]<<",and ";
        }
        else
        {
            cout<<num_vec[z]<<", ";
        }   
    }

    return 0;
}

Answer 1

I would use std::getline() to read the user's entire input in one go, and then use std::istringstream to parse it, eg:

#include <iostream>
#include <string>
#include <sstream>
#include <vector>
#include <algorithm>

void get_nums(std::vector<int> &num_vec)
{
    std::string line, tokens;

    std::getline(std::cin, line);
    std::istringstream input(line);

    while (std::getline(input, tokens, ','))
    {
        std::istringstream values(tokens);
        int num;

        if (!(values >> num))
            continue;

        values >> std::ws;
        char ch = values.peek();

        if (ch == '-')
        {
            values.ignore();

            int num2;
            if (!(values >> num2))
                continue;

            while (num <= num2)
                num_vec.push_back(num++);
        }
        else if (ch == std::char_traits<char>::eof())
            num_vec.push_back(num);
    }
}

int main()
{
    std::vector<int> num_vec;

    std::cout << "\n Please, enter your HW: " << std::flush;
    get_nums(num_vec);

    if (!num_vec.empty())
    {
        std::sort(num_vec.begin(), num_vec.end());

        std::cout << "\n Do Problems: ";

        std::cout << num_vec[0];

        for(int z = 1; z < num_vec.size(); ++z)
        {
            std::cout << ", ";

            if ((z+1) == num_vec.size())
                std::cout << "and ";

            std::cout << num_vec[z];
        }
    }
    else
        std::cout << "\n No Input! ";

    return 0;
}

Input: 25,1,3-6
Output: 1,3,4,5,6,25

Input: 25,1,3 - 6
Output: 1,3,4,5,6,25

Input: 2 5, 1 , 3- 6
Output: 1,3,4,5,6 ¹

¹: 2 5 is not valid input in this code. If you want it to be, you will have to add some extra code to handle space-delimited numbers in addition to comma-delimited numbers.