Read a txt file into a multi variable dimension array in c++

Question

I've the need of read a txt file that is structured in this way

0,2,P,B
1,3,K,W
4,6,N,B
etc.

Now I need to read in an array like arr[X][4]
The problem is that I don't know the number of lines inside this file.
In addition I'd need 2 integers and 2 char from it...

I think I can read it with this sample of code

ifstream f("file.txt");
while(f.good()) {
  getline(f, bu[a], ',');
}

obviusly this only shows you what I think I can use....but I'm open to any advice

thx in advance and sry for my eng

hmjd · Accepted Answer · 2012-09-17 10:50:19Z

5

Define a simple struct to represent a single line in the file and use a vector of those structs. Using a vector avoids having to manage dynamic allocation explicitly and will grow as required.

For example:

struct my_line
{
    int first_number;
    int second_number;
    char first_char;
    char second_char;

    // Default copy constructor and assignment operator
    // are correct.
};

std::vector<my_line> lines_from_file;

Read the lines in full and then split them as the posted code would allow 5 comma separated fields on a line for example, when only 4 is expected:

std::string line;
while (std::getline(f, line))
{
    // Process 'line' and construct a new 'my_line' instance
    // if 'line' was in a valid format.
    struct my_line current_line;

    // There are several options for reading formatted text:
    //  - std::sscanf()
    //  - boost::split()
    //  - istringstream
    //
    if (4 == std::sscanf(line.c_str(),
                         "%d,%d,%c,%c",
                         &current_line.first_number,
                         &current_line.second_number,
                         &current_line.first_char,
                         &current_line.second_char))
    {
        // Append.
        lines_from_file.push_back(current_line);
    }

}

edited Sep 17, 2012 at 10:50

answered Sep 17, 2012 at 10:31

hmjd

122k21 gold badges216 silver badges259 bronze badges

Sign up to request clarification or add additional context in comments.

1 Comment

Fed03 Over a year ago

ty @hmjd this is exactly what I'm looking for. I was thinking abuot struct but I didn't know how to integrate it into vectors^

Collectives™ on Stack Overflow

Read a txt file into a multi variable dimension array in c++

1 Answer 1

1 Comment

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

1 Answer 1

1 Comment

Your Answer

Sign up or log in

Post as a guest

Related