How to make user input declare the size of string array?

Question

something like

ifstream myfile ("example.txt");
        if (myfile.is_open())
        {
            while ( getline (myfile,line) )
            {
                nr++; //how many lines in a text file
            }
        }

string y[nr] = {};

only works when I specify actual number like y[10].

The user cannot "declare" the array. Only the programmer can. — user3920237
– user3920237, Commented Feb 3, 2015 at 20:54
Related: Does C++ support Variable Length Arrays? and Variable length arrays in C++? The latter probably makes this question a duplicate. — jww
– jww, Commented Feb 3, 2015 at 21:10

NathanOliver · Accepted Answer · 2015-02-03 21:00:09Z

3

You cannot declare arrays with an unknown size unless you are using a non portable compiler extension. The standard way to accomplish this is to use a vector.

int x;
cout << "Size of your array: ";
cin >> x;
vector<string> y(x);

answered Feb 3, 2015 at 21:00

NathanOliver

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2 Comments

jww Over a year ago

Variable-length automatic arrays are allowed in ISO C99. As an extension, GCC accepts variable-length arrays as a member of a structure or a union. See GCC's 6.19 Arrays of Variable Length.

NathanOliver Over a year ago

@jww Thanks for mentioning that. Since it was tagged as c++ I didn't want to mention C99.

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