How do you insert and integer in a string array?

Question

This has worked for several of my classmates. It runs with no error, but ends at  if (arr [r][c] == "[L]").

What else can I use to keep the brackets, but replace L with an incremented number?

int num=1;
for (int r = 0; r <= ROWS; r++)
    {
        for (int c = 0; c <= COLS; c++)
        {
            if (arr [r][c] == "[L]")
            {
                string str = to_string(num++);
                string s = "[" + str + "]";
                arr[r][c] = s;
            }
        }
    }

Answer 1

This should work

int number = 3; // use your own value
// ...
if (arr [r][c] == "[" + to_string(number) + "]")