How Many Times a Char is Repeated in a String ? [String Subscript Out of Range Error]

Question

Here's my Code to count how many times a char is repeated in a string :

int count_char(string a, char b)
{
    int size = sizeof(a) / sizeof(a[0]);
    int counter = 0;
    for (int i = 0; i < size; i++)
    {
        if (a[i] == b)
        {
            counter++;
        }
    }
    cout << a << "has " << counter << b << "s\n";
    return counter;
}
int main()
{
    count_char("Hello", 'l');
}

For me , everything looks good but Microsoft Visual Studio seems to see something else , this is what I got:

Can anyone see where's the problem ?

Answer 1

The sizeof trick you are trying to use works only on a fixed-size array, not on a std::string object.

std::string has several data members, including the data pointer, the length and capacity counters, the SSO buffer (if there is one), etc. Your character data contains only 5 characters, but the size of the std::string class is much more than that, hense why you are going out of bounds on the iteration.

To get the correct character size, use the string's size() (or length()) method instead:

size_t size = a.size(); // or .length()

That being said, you don't need to count the characters manually. You can use the standard std::count() algorithm instead:

#include <algorithm>

size_t counter = std::count(a.begin(), a.end(), b);