Question

I’ve looked around a bit and have found no definitive answer on how to read a specific line of text from a file in C++. I have a text file with over 100,000 English words, each on its own line. I can’t use arrays because they obviously won’t hold that much data, and vectors take too long to store every word. How can I achieve this?

P.S. I found no duplicates of this question regarding C++

while (getline(words_file, word))
{
    my_vect.push_back(word);
}

EDIT:

A commenter below has helped me to realize that the only reason loading a file to a vector was taking so long was because I was debugging. Plainly running the .exe loads the file nearly instantaneously. Thanks for everyones help.

Answer 1

If your words have no white-space (I assume they don’t), you can use a more tricky non-getline solution using a deque!

using namespace std; 

int main() {
    deque<string> dictionary;

    cout << "Loading file..." << endl;
    ifstream myfile ("dict.txt");
    if ( myfile.is_open() ) {
        copy(istream_iterator<string>(myFile),
             istream_iterator<string>(),
             back_inserter<deque<string>>(dictionary));
        myfile.close();
    } else {
        cout << "Unable to open file." << endl;
    }

    return 0;
}

The above reads the entire file into a string and then tokenizes the string based on the std::stream default (any whitespace – this is a big assumption on my part) which makes it slightly faster. This gets done in about 2-3 seconds with 100,000 words. I’m also using a deque, which is the best data structure (imo) for this particular scenario. When I use vectors, it takes around 20 seconds (not even close to your minute mark — you must be doing something else that increases complexity).

To access the word at line 1:

cout << dictionary[0] << endl;

Hope this has been useful.