Array element never successfully added? (C++)

Question

I'm fairly new to C++. I tried implementing a really simple hash table, and then I wanted to see if my hashing algorithm put the element in the correct position. However, apparently the element wasn't even added to the array at all:

void add(string str, array<string, 2000> data) {
    int i = makeHash(str) % data.size();

    while (data[i++ % data.size()].compare("") != 0)
        continue;

    data[i % data.size()] = str;
    cout << "Added!"; // successfully prints, meaning str was added to data
}

int main() {

    array<string, 2000> data;
    string str = "The quick brown fox something something";
    add(str, data);

    for (int i = 0; i < data.size(); i++)
        if (data[i].compare(str) == 0)
            cout << i; // never prints... so str was never added to data?

    return 0;
}

Answer 1

You need to pass data variable as reference -

void add(string str, array<string, 2000> &data)

What you are doing here is pass by value, so as soon as your function ends, value of data is destroyed.

Answer 2

Try passing data by reference, i.e.

void add ( string str, array<string, 2000>& data ){...}

Passing by value will mean a copy of data will be passed into the function. Also, there's an off by one error. I'm sure you want to have:

data[(i-1) % data.size()] = str;

because i will still be incremented when you exit the while loop.