reading string text input to create a 2D Vector

Question

Given a regular text file of:

56789
28385
43285
22354
34255

I am trying to read each string character in the text file and store them in a 2D vector.

First I would like to take each string row. Then I would like to take each character in the row and convert into an int then push_back into the row. Then I'd like to repeat for each line.

When outputting each column and row in my 2D vector, I would like the same exact output of:

56789 //each number an int now instead of a string
28385
43285
22354
34255

My issue is that I try to use i = stoi(j); which gives the error:

No matching function for call to 'stoi'

I do have the correct #include to be able to use stoi()

vector<vector<int>> read_file(const string &filename) 
{
    string file, line; stringstream convert; int int_convert, counter;
    vector<vector<int>> dot_vector;

    file = filename;
    ifstream in_file;
    in_file.open(file);

    while (getline(in_file, line)) {
        counter++; //how many lines in the file
    }

    char current_char;
    while (getline(in_file, line)) {
        for (int i = 0; i < counter; i++) {
            vector<int> dot_row;
            for (int j = 0; j < line.size(); j++) {
                current_char = line[j];
                i = stoi(j); //this is giving me an error
                dot_row.push_back(i);
            }
            dot_vector.push_back(dot_row);
        }
    }

    in_file.close();
    return dot_vector;
}

Answer 1

Here

 i = stoi(j);
 // j is integer already

std::stoi expect a string as the argument and what you providing is an int.

You can either convert the char to string and call std::stoi like follows

std::string CharString(1, line[j]);
dot_row.emplace_back(std::stoi(CharString));

or can convert the char to int directly while keeping to the vector:

dot_row.emplace_back(static_cast<int>(line[j] - '0'));

---

You have other problems in your code. Like in the comments mentioned, you do not need the extra counting of lines. Once you have your first while loop, you will reach already end of your file. The code after is then meaningless.

Secondly, you do not need two for loops. Simply use a range-based for loop for each line of strings and while iterating through it, convert to integer and save to vector.

while (getline(in_file, line)) 
{
    std::vector<int> dot_row; dot_row.reserve(str.size());
    for (const std::string& eachChar: line) 
    {
        std::string CharString(1, eachChar);
        dot_row.push_back(std::stoi(CharString));
        // or other option mentioned above
    }
    dot_vector.push_back(dot_row);
}