Question

#include <iostream>
#include <fstream>
#include <sstream>
#include <string>
#include <vector>
using namespace std;

int main()
{
    ifstream inFile("test.txt");
    string line;

    while(getline(inFile, line))
    {
        istringstream meh(line);
        int n;
        vector<int> v;

        while(meh >> n)
            v.push_back(n);
    }
}

My test.txt file looks like:

429384
392041
230138
099938
243324

If I try to print v[0] I get the entire sequence of numbers back (42938…3324) instead of just the first number 4. Can anyone explain why this is happening?

Answer 1

You probably made a mistake when you output your data.Your code stores in fact only one int-value for each line – the whole line was stored inside v[0]. Then you wrote that whole number inside a stream and forgot to write a new line before your while-loop started to process the next line. Thus, your output was one large number.

#include <iostream>
#include <fstream>
#include <sstream>
#include <string>
#include <vector>
using namespace std;

int main()
{
    istringstream inFile("text.txt");
    string line;
    vector<vector<int> > vector_container;

    while(getline(inFile, line))
    {
        istringstream meh(line);
        char n;
        vector<int> v;

        while(meh >> n)
            v.push_back(static_cast<int>(n)-48);

        vector_container.push_back(v);
    }
    // this would output your numbers the way they were
    // stored inside your file
    for(int i = 0; i < vector_container.size(); ++i){
        for(int j = 0; j < vector_container[i].size(); ++j){
             cout << vector_container[i][j];
        }
        cout << endl;
    }

}

This should work the way you expected it to be. You will have a vector<int> container inside a vector<vector<int> >. The first one will store your number in a line, whereas each character will be stored individually. The latter vector simply stores the vectors for the numbers for your lines. The char to int conversion should explain itself when you take a look at the ASCII-table.