C++ - Using stringstream object to read strings and integers from a sentence in an external txt file

Question

I tried to retrieve the integers from a txt file and adding them up to get the total. I did this using stringstream class. The string of the text is:- 100 90 80 70 60. The code to extract the integers and add them is as follows:-

#include<iostream>
#include<fstream>
#include<sstream>
using namespace std;
int main(void)
{
    ifstream inFile("C:\\computer_programs\\cpp_programs\\exp6.txt",ios::in);
    stringstream sstr;
    string from_file;
    int grade;
    int total = 0;
    getline(inFile,from_file);
    sstr<<from_file;
    while(sstr
    {
        sstr>>grade;
        cout<<grade<<endl;
        total+=grade;
    }
    cout<<total<<endl;
    inFile.close();
    return 0;
}

This code works fine. After this, I modify the string in the file as 'the grades you scored are 100 90 80 70 60`. Now, if try to run the above code, I get the output as:-

0
0
0
0
0
0

Can you please help me and tell me how to calculate the total in the latter case ? Also, here I know the number of integers in the files. What about the case when I don't know the number of grades in the file?

Answer 1

Because "the grades you scored are " is the head part of your stringstream.

You cannot get read an int from it. It'll just give you a 0

You may read to some string as "Entry" and parse the Entry by writing some functions.

Answer 2

I'll be answering the second part of the question i.e. reading inputs without knowing the total number of inputs:-

#include<iostream>
#include<fstream>
#include<sstream>
using namespace std;
int main(void)
{
    ifstream inFile("C:\\computer_programs\\cpp_programs\\exp6.txt",ios::in);
    string data;
    int grades,total=0;
    getline(inFile,data);
    stringstream sstr;
    sstr<<data;
    while(true)
    {
        sstr>>grades;   
        if(!sstr)
            break;
        cout<<grades<<endl;
        total+=grades;
    }
    cout<<total<<endl;
    return 0;
}